zoologicol Journal of ihc Linnean SocieQ (1993), 109: 275-299. With 4 figures
The systematic relationships of the snake
genus Anornochilus
DAVID CUNDALL*
Behavioral and Evolutionary Biosciences, 17 Memorial Drive East, Lehigh University,
Bethlehem, P A 18015-3007, U . S . A .
V. WALLACHt AND DOUGLAS A. ROSSMAN
Museum of Natural Science, Louisiana State University, Baton Rouge, L A 70803-3216,
U.S.A.
Received September 1992, accepted for publication April 1993
Phylogenetic analysis of 38 skeletal characters, 12 muscular characters and 15 visceral characters in
17 major snake clades plus Anornochilur suggests that Anornochilur is the sister taxon of all other living
alethinophidian snakes. However, skeletal, muscular and visceral character sets analysed separately
or in pairs give four groups of nonconcordant tree topologies. Based on the cladogram derived from
the total evidence, two families are erected to prevent the existing family Uropeltidae from
becoming paraphyletic: Anomochilidae, for the Malaysian and Indonesian genus Anomochilus, and
Cylindrophiidae, for the Sri Lankan, Southeast Asian and Indonesian genus Cylindrophis and the
Upper Eocene fossil Eoanilius.
ADDITIONAL KEY WORDS:-Serpentes
muscles.
phylogeny
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-
systematics
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skeleton - visceral
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CONTENTS
Introduction . . . . . . .
Materials and methods
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Character list
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Results . . . . . . . .
Discussion and systematic conclusions .
Acknowledgements
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References
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INTRODUCTION
In the preceding paper within this issue (pp. 235-273), Cundall & Rossman
( 1993) describe the cephalic anatomy of a single specimen of the rare Indonesian
snake Anomochilus weberi, comparing it primarily to scolecophidian, uropeltine
*Correspondence to D. Cundall
?Present address: 4 Potter Park, Cambridge MA02138, U.S.A.
275
0024-4082/93/011275 +25 S08.00/0
0 1993 The Linnean Society of London
D. CUNDALL ET AL.
276
and cylindrophiine snakes. This paper considers the systematic relationships of
Anomochilus based on cephalic bone and muscular features, as well as visceral
characters derived from the studies of one of us (VW).
The genus Anomochilus includes two species of small, presumably fossorial
snakes from Indonesia and Malaysia. The genus was erected by Lidth de Jeude
(1890) for a single female specimen, collected by Max Weber at Kaju Tanam,
Sumatra, in 1888 and named Anomalochilus weberi. Berg (1901) pointed out that
the name Anomalochilus was preoccupied by a coleopteran and proposed the
substitute name Anomochilus for the snake. A second female specimen of A . weberi
was collected in the Padang highlands of Sumatra (Lidth de Jeude, 1922) and a
third female in Kutei, Borneo (Brongersma & Helle, 1951).
A second species of Anomochilus, A. leonardi, was described by Smith (1940) on
the basis of two female specimens collected by G. R. Leonard at Sungei Ngeram
and Kuala Tahan in Pahang, Malaysia. A third specimen of A. leonardi from the
Ulu Gombak Forest Reserve, Selangor, Malaysia, was recorded by Lim &
Mohd. Sharef bin Kamarudin (1975). No other specimens have been reported
and thus the genus currently contains two species, each known from only three
Figure 1. Lateral (A), dorsal (B), and ventral (C) views of the head of Anomochilus weberi (RMNH
9507).
ANOMOCHILUS RELATIONSHIPS
277
TABLE
1. Selected features of Anomochilur specimens. Abbreviations: DSR, number
of dorsal scale rows; H, holotype; IMR, Institute for Medical Research, Division of
Medical Ecology, Kuala Lumpur, Malaysia; SC, number of subcaudals; SVL and
TL, snout-vent lengths and total lengths in mm; Ven, number of ventrals
Species
Catalogue no.
A . lconardi
BM 1946.1.17.4 (H)
BM 1959.1.2.63
IMR 103298
RMNH 4329 ( H )
RMHN 4691
RMHN 9507
A.
A.
A.
A.
A.
lconardi
Ieonardi
webcri
webcri
wcberi
Sex
DSR
Ven
SC
SVL
TL
F
F
17-17-15
17-17-17
17
17-19-17
17-19-17
17-19-17
222
223
214
236
248
239
6
7
6
8
7
6
265
217
271
224
I72
362
~
F
F
~
352
~
306
315
specimens. Four of these specimens, including both types, were examined during
this study, although most cephalic and visceral anatomical data are derived from
dissection of a single specimen of A . weberi.
Both species are small, cylindrical-bodied snakes having rounded heads (Fig.
1) and short tails (Table 1). Both have features plesiomorphic for snakes (pelvic
vestiges, simple superficial palate, tracheal lung absent, oviparity) and have
reductions or losses characteristic of primitive, fossorial snakes (head scales
reduced in number, eye size reduced, spectacle reduced or absent, ventrals
reduced, mental groove absent, left lung absent, premaxilla and palatal bones
edentulous: Lidth de Jeude, 1890; Brongersma & Helle, 1951; Groombridge,
1979b). O n these grounds, Anomochilus has traditionally been allocated to the
Aniliidae (Lidth de Jeude, 1890; Boulenger, 1893). Romer ( 1956), apparently
with some uncertainty, placed both Anomochilus and Cyfindrophis in his subfamily
Uropeltinae of the family Aniliidae. Underwood ( 1967) allied Anomochilus with
Cyfindrophis and Anifius but not uropeltines, whereas McDowell ( 1975) suggested
that Anomochilus may be most closely related to Cyfindrophis and, in his reviews of
snake systematics (McDowell, 1975, 1987), placed Anomochilus with Cyfindrophis
in the subfamily Cylindrophiinae of the family Uropeltidae. Groombridge
(1979b), on the basis of a variety of anatomical features, supported McDowell’s
( 1975) proposal that Cyfindrophis and Anilius were more widely separated than
previously thought and Groombridge also aligned Anomochilus with the former.
Distant separation of Cylindrophis and Anifius and a close relationship between
Cyfindrophis and uropeltines has been supported by more recent immunological
data (Cadle et al., 1990). Rieppel (1977a, 1979c, d), on the other hand, favoured
the ‘evolutionary hypothesis’ that uropeltines (his Uropeltidae) are the sister
group to aniliids, comprised of aniliines (Anifius) and cylindrophiines
(Cylindrophis and Anomochilus). Thus, the weight of evidence and opinion when we
began our studies allied Anomochilus to Cylindrophis, but no consensus existed on
the relationships among the various primitive snakes traditionally included in
the Anilioidea.
MATERIALS AND METHODS
Preliminary hypotheses of the phylogenetic relationships of Anomochilus were
formulated from binary and multistate cephalic characters analysed using PAUP
278
D. CUNDALL E l AL.
Version 3.1.1 (Swofford, 1993). Taxa entered in the analysis are listed below and
follow the arrangements of McDowell (1987) and Estes et al. (1988). For most
taxa of higher rank (genus and above), information on cephalic anatomy is
available for only a few of the included species. Visceral data are based on
representatives of most scolecophidian and lower alethinophidian genera plus
selected colubroid genera. Character states and their distribution among the
taxa were drawn from examination of specimens and from the following sources:
anguimorphs-Camp (1923), McDowell (1972), McDowell & Bogert (1954),
Estes et al. (1988); dibamids-Gasc (1968), Rieppel (1984), Greer (1985), Estes
el al. ( 1988); scolecophidians-Haas
( 1930a, 1959, 1962, 1964, 1968, 1973),
Evans ( 1955), Brongersma ( 1958), List ( 1966), Underwood ( 1967), McDowell
(1967, 1972, 1974a, 1987), Langebartel (1968), Groombridge (1979c), Rieppel
(1930b, 1973),
(1979a, 1980b, c); Anilius and cylindrophiines-Haas
Langebartel (1968), Rieppel (1977a, b, 1979b, 1980a, b), Groombridge (1979a);
uropeltines-Baumeister
(1908), Haas (1930b), Rieppel (1978a, 1979b,
1980a, b); Xenopeltis and Loxocemus-Haas
( 1930b, 1955, 1973), McDowell
(1975, 1987), Rieppel (1977a, 1979b); pythonids-Frazzetta (1959, 1966, 1975),
McDowell (1975), Underwood (1976), Underwood & Stimson ( 1990); boinesBeddard (1906, 1909), Frazzetta (1959, 1975), McDowell (1979), Kluge (1991);
erycines-Haas (1930b), Langebartel ( 1968), Rieppel (1978b); bolyeriidsAnthony & Guibi: (1952), Frazzetta (1970, 1971), McDowell (1975, 1987),
Cundall & Irish (1989); tropidophiids-McDowell ( 1975, 1987); acrochordidsHaas (1931), Hoffstetter & Gayrard (1965), Groombridge (1979a), McDowell
( 1979, 1987); colubroids-primarily
personal observations, plus Haas ( 1930b,
1931, 1973), Underwood ( 1967), Langebartel ( 1968), Bourgeois ( 1968),
McDowell (1972, 1975, 1986, 1987), Groombridge (1979a), and Rossman et al.
(19821.
'
Our choice of outgroups was based on recent analyses of squamate phylogeny
by Estes et al. (1988). Their Wagner tree placed snakes in the Anguimorpha as
the sister taxon of helodermatids and varanids. In this tree, dibamids and
amphisbaenians are sister taxa, and together they represent the sister taxon of
the snake, helodermatid and varanid clade. PAUP analysis of the same data
produced a tree (described but not illustrated) in which snakes and
amphisbaenians are sister taxa; these two together are sister taxa of Gekkota and
dibamids, and all four are sister taxa of anguimorphs. Similarities among the
three limbless clades (snakes, dibamids, and amphisbaenians) were ascribed, in
part, to convergences associated directly with limb loss and indirectly with the
behavioural ecology of these clades and their immediate ancestors. As a result,
Estes et al. (1988) preferred a more conservative hypothesis of squamate
phylogeny, in which snakes, dibamids and amphisbaenians are placed as
Scleroglossa, incertae sedis. The conclusion that snakes cannot be placed in any
clade less inclusive than Scleroglossa makes it difficult to define appropriate
outgroups. Initial efforts to compare Anomochilus and other snakes to
autarchoglossan (scincomorph and anguimorph) lizards suggested that, for our
characters, scincomorphs and anguimorphs are very similar. We used
anguimorphs as our ancestral outgroup. Because many of the 'lower' snake
taxa are fossorial, we included data on dibamids to determine how our
characters distributed these highly specialized fossorial lizards in comparison
with the various clades of fossorial snakes.
ANOMOCHILUS RELATIONSHIPS
279
We entertain few illusions about our current ability to test rigorously, and
a priori, the homology of characters shared among the diverse taxa examined
here. We have accepted a number of characters that have been used previously
(sources noted in character descriptions below) and trust that our interpretation
of these characters conforms to prior usage. We follow Patterson (1982) and
Kluge (1991) in placing emphasis on synapomorphies rather than homologies.
With regard to ‘primitive’ snakes, identifying outgroups that contain a
reasonably complete assemblage of character states primitive to those found in
snakes has proved very difficult, as noted by previous workers (e.g. Rieppel,
1979c, 1988a, b; McDowell, 1987; Estes et al., 1988) who have tried to provide
consistent hypotheses of evolutionary direction for character transformations.
For this reason, multistate characters were treated as unordered (nonadditive).
For binary characters, the condition in anguimorphs was designated as the
ancestral state. Taxa having more than one state for a character were entered as
polymorphic. In those few cases in which anguimorphs were polymorphic for a
character, the ancestral state was that either most common in anguimorphs
alone or most common in anguimorphs and scincomorphs.
We have used character loss or absence as an apomorphic state for a number
ofcharacters (4, 9, 16, 23, 35, 36, 37, 38, 42, 43, 49, 50, 52, 54, 56; see character
descriptions and Table 2). This usage carries with it a number of problems.
Whereas reduction may be associated, either empirically or theoretically, with
one or more causal factors, these factors usually cannot be invoked to explain
loss. (Selection favouring decrease in size should act primarily by regulating
relative size. The appearance or disappearance of a structure presumably could
be, and probably would be, under separate regulatory control.) Additionally,
there are numerous demonstrations that certain structures fail to appear (or have
been lost) in clades that, on all other grounds, are phyletically unrelated (e.g.
some morphological features used to assess relationships among
salamanders-Duellman
& Trueb, 1986). Snakes have long been defined by
losses of structures, and our use of losses as apomorphies for this group continues
this tradition. Hecht & Edwards ( 1977) suggested that characters representing
loss of a feature should receive the lowest weighting in their character weighting
scheme if there was no ontogenetic data to indicate how the loss occurred and,
hence, no way to show that loss synapomorphies are homologous. Because we
suspected that the use of losses as apomorphies might increase the level of
homoplasy in the data and influence tree structure, we compared trees produced
by all of the characters (total evidence: Kluge, 1989) with trees produced by a
data set that excluded all loss characters. Our ultimate systematic conclusions
are based on the total evidence.
Character list
Skeletal characters
( I ) Premaxilla. Articulation to nasals: primarily through an ascending process
that abuts or lies between the horizontal laminae of the nasals (0), by a
transversely expanded ascending process that meets the horizontal laminae of
the nasals ( l ) , primarily through the processus nasalis that extends between the
ventral edges of the nasals (2), absent ( 3 ) . Comment. States of the premaxilla are
not readily generalized, because the bone displays extraordinary variation. A
280
D. CUNDALL ET AL.
critical and as yet unresolved issue is the homology of the median dorsal and/or
caudal processes (see Char. 2). Most lizards appear to have state 0. In varanids,
a process that appears homologous to the nasal process of pythons extends
beneath the fused nasals to contact the frontals. In colubroid snakes,
premaxillary contacts with the nasals vary considerably because snout bones in
this clade have relationships quite different from those in other clades. This
difference is reflected in complete loss of contact between the premaxilla and
nasals in some taxa, although most taxa have what is ascribed above as the
plesiomorphic state for squamates. All hypotheses of the phylogeny of snakes
would require that the colubroid possession of state 0 be secondarily derived.
Whereas the dorsal articulation of the premaxilla with the nasals may be
markedly similar in anguimorphs and colubroids, other premaxillary
relationships differ.
(2) Premaxilla. Processus nasalis: absent or present as a keel not lying between
nasals (0), well developed and lying between nasals (1). Comment. Frazzetta
(1975) defined the nasal process of the premaxilla as the structure characteristic
of Python extending between the ventral edges of the vertical laminae of the
nasals. The boine ascending process, which contacts the anterior tips of the
horizontal laminae of the nasals, Frazzetta considered to be a homologue of the
nasal process in pythons ". . . it thus appears likely that the boine ascending
process is actually the pythonine nasal process rotated 90" in evolution." Kluge
(1991) interpreted some boines (e.g. Candoia) as retaining a nasal process as well
as having an ascending process, but he considered the advanced snake clade to
lack an ascending process. Our interpretation is that the premaxilla of most
snakes has an ascending process (associated with the rostra1 gland and
connecting to the anterodorsal ends of the nasals) and a nasal process that
extends to, or lies betweeen, the anteroventral edges of the nasals or, as in some
colubroids, the septomaxillae. This interpretation emphasizes relationships
between premaxillary parts and surrounding hard and soft structures rather
than the orientation and geometry of the premaxilla in three-dimensional space.
On this basis, most advanced snakes possess both processes; hence, the ascending
process of boines is not homologous to the nasal process of pythonids. In fact, we
consider both boines and pythonids to have both processes. In most pythonids,
the ascending process is highly reduced and does not meet the anterodorsal tips
of the nasals, whereas in boines the nasal process is reduced.
(3) Premaxilla. Vomerine (palatine) process or caudoventral edge: overlaps
vomer ventrally (0), meets vomer (or septomaxilla) ( l ) , does not meet vomer
(2). Comment. State 2 may represent either caudal displacement of the vomer or
reduction of the vomerine process. This character, adapted from Underwood's
(1976) character 38, is difficult to code reliably from information in the literature
because the snout of most snakes is sufficiently loose to permit some changes in
relative positions of premaxilla and vomers. Our assignment of character states
for more diverse taxa represents a first approximation.
( 4 ) Premaxilla. Teeth: present ( 0 ) , absent (1). Comment. Egg tooth not counted.
(5) Nusuls. Nasofrontal articulation: nasals overlap frontals dorsally (0), frontals
overlap nasals dorsally ( l ) , dorsal surfaces of nasals and frontals separated and
non-overlapping (2). Comment. This is Kluge's ( 1991) character 14 modified to
accommodate the scolecophidian condition described by Haas ( 1930a).
(6) Vomeronasal cupola: fenestrated medially (0), not fenestrated medially (1).
ANOMOCHILUS RELATIONSHIPS
28 1
( 7 ) Frontals. Interolfactory pillar: absent (0), frontal flanges present, unfused, or
with fusion line obvious ( l ) , frontal flanges fused with no fusion line (2). Comment.
Underwood (1967) and McDowell ( 1967) noted the significance of this
character and our coding follows states defined by Underwood (1976) and
Rieppel (1978a).
(8) Prefrontal. Limited to anterior orbital region and/or extends between frontal
and maxilla (0), sutured between frontal, nasal, and maxilla ( l ) , movably
articulated to frontal and maxilla but extended anteriorly between nasal and
maxilla (2). Comment. Contact between the prefrontal and nasals appears to be a
primitive squamate feature lost in scincomorphs and, presumably, ancestral
anguimorphs (Estes et al., 1988). Snakes show a range of prefrontal relationships
which are difficult to simplify and, hence, difficult to code. Most colubroids have
the primitive condition. States 1 and 2 appear to represent different structural
approaches to strengthening or supporting the snout. Our interpretation is based
on McDowell (1975:9).
(9) Postorbital: present ( 0 ) ,absent (1).
(20) Supraorbital: absent ( 0 ) ,present (1). Comment. Bellairs & Kamal (1981) and
Underwood & Stimson (1990) extended Rieppel’s (1997a) intepretation of the
postfrontal of uropeltids (see Char. 11) to include the bone in Loxocemus and
pythonids long referred to as a supraorbital. We have retained supraorbital here
because there remains little empirical support for the homology of the two
structures. If the bone is actually a postfrontal, then anguimorphs and dibamids
should both be recoded as polymorphic for this character.
(22) Parietal. Supraorbital process: not enlarged (0), enlarged, extending along
at least 50% of the lateral border of the frontal (1). Comment. This structure has
been referred to as a postfrontal by Rieppel (1977a) and a supraorbital by
McDowell (1987). In the absence of developmental data, the actual homology of
the structure remains problematic. A similar structure is present in some
colubroid taxa (e.g. Miodon, Aparallactus: Bourgeois, 1968; Atractus: Irish, pers.
comm.) and may be associated with fossoriality, although it also appears in
many marine hydrophiines (Smith, 1926; McDowell, pers. comm.) .
(22) Frontoparietal suture: partially open, potentially mobile (0), closed, immobile
(1). Comment. McDowell (1974a, 1979) discussed this character and suggested
that the mobile condition could be achieved secondarily and did not represent a
primitive condition, at least in acrochordids.
(23) Frontal-prefrontal sutures: widely separated medially (0), not widely
separated medially (1). Comment. Underwood (1976) used a character similar to
this (his character 39) and with the same polarity but with three states defined
by the width of the gap between prefrontals relative to the total width of the
anterior edge of the frontals.
(24) Prootic. Laterosphenoid: absent ( 0 ) ,present and separating V, and V, (1).
Comment. Underwood (1967) used this character, although it displays more
variability than is commonly acknowledged. The laterosphenoid is missing, for
example, in some specimens of Python (pers. obs.) and Bolyeria (Irish, pers.
comm.) as well as some specimens of various colubroid genera (Heterodon,
Xenodon, Trimeresurus, Bothrops: Gibson, 1972; Opheodrys: Cundall, 1973),
although it does not appear to be uniformly lost in any alethinophidian clade.
(25) Exoccipital. Fenestra pseudorotunda: absent (0), present ( 1). Comment.
Rieppel ( 1979b) showed that in aniliids, cylindrophiines, and uropeltines the
282
D. CUNDALL E l AL.
perilymphatic system reaches the juxtastapedial sinus by passing from the
perilymphatic foramen into a recess in the opisthotic that exits through a
fenestra pseudorotunda dorsal to the apertura lateralis. Exactly how this changes
the form of the perilymphatic system was not illustrated, although in other
snakes the perilymphatic sac apparently leads to the juxtastapedial sinus by
passing through the apertura lateralis. McDowell ( 1987) ascribed the differences
to posterior extension of the fenestra ovalis into the recessus scala tympani and he
considered Xenopeltis and Loxocemus to have a condition similiar to that of
anilioids sensu Rieppel (1988a). Anomochilus has what appears to be a foramen
pseudorotunda as well as an apertura lateralis, but confirmation was not possible
without disarticulating the skull.
(16) Supratemporal: present ( 0 ) , absent (1). Comment. Polarity and homology are
after Estes et al. (1988).
(17) Parasphenoid. Interchoanal process: absent (0), present ( I ) . Comment. The
anterior end of the parasphenoid forms a pointed or plate-like process below the
trabeculae in most snakes, but this process does not extend ventrally between the
choanal processes of the palatine except in those taxa noted.
(18) Palatine. Teeth: absent ( 0 ) ,present (1). Comment. A number of anguimorphs
consistently have palatine teeth (Estes el al., 1988), although most do not. That
taxon is therefore coded as polymorphic. However, because only some specimens
of one uropeltine species, Melanophidium punctatum, have palatine teeth (Rieppel,
1977a), uropeltines were assigned the plesiomorphic condition. Character
polarity is drawn from Estes et al. (1988).
(19) Palatine. Subvomerine process: absent (0), present ( 1). Comment. This
process extends the palatine anterior to the caudal edge of the vomer. It appears
to be a synapomorphy of alethinophidian snakes (Underwood, 1967; Rieppel,
1988a, b) ,
(20) Palatine. Choanal process articulation with caudal edge of vomer: simple
(0), complex ( I ) , absent (2). Comment. Unlike binary characters that have
absence as the derived state, this multistate character and others having absence
as one of three or more conditions were entered as unordered because loss is not
considered here to be part of a transformation series. Thus, all multistate
characters with loss as one alternative (22, 31, 32, and 42, but not 21) assume
that at least two transformation processes are at work on the character, one or
more sets dealing with elaboration or reduction, one set resulting in loss. For this
particular character, what is lost is a tight association between vomer and
palatine, resulting in much greater potential freedom of motion of the palatine.
State 2 could therefore be interpreted as a gain of soft tissues in the joint space
(permitting increased mobility), instead of absence of articulation.
(21) Palatine. Articulation with maxilla: suture (0), interlocking joint preventing
longitudinal displacement ( l ) , simple gliding joint (2), no articulation (3).
Comment. The nature of the reorganisation of soft tissues for state 3 remains
undescribed in most taxa. If the palatines lie well removed from the maxillae,
state 3 is assigned regardless of whether the palatines lie perpendicular
(anomalepidids: Haas, 1964, 1968; List, 1966) or parallel (colubroids: Bourgeois,
1968) to the maxillae.
(22) Ectopterygoid. Present and in contact with both maxilla and pterygoid (0),
present but not in contact with pterygoid ( I ) , present but in contact with neither
pterygoid nor maxilla (2), absent (3). Comment. The coding of this character may
suggest a transformation series in which states 1 and 2 are evolutionarily
ANOMOCHILUS RELATIONSHIPS
283
intermediate between 0 and 3. Anomochilus could be considered intermediate
between typical squamate conditions, in which the ectopterygoid is either a
mobile (most Alethinophidia) or a fixed (most lizards) link between pterygoid
and maxilla, and the scolecophidian conditions, in which the ectopterygoid is
either missing (typhlopids) or reduced to a small element tightly attached to the
maxilla and palatine. However, the scolecophidian conditions seem more
complex than these simple descriptions suggest (Dunn & Tihen, 1944; McDowell
& Bogert, 1954; List, 1966), and a fundamental feature of the scolecophidian
ectopterygoid, where it is clearly present (anomalepidids, leptotyphlopids) , is
that it contacts the maxilla. Interpreting the ectopterygoid of Anomochilus as a
stage in the reduction of the bone leading to its loss in typhlopids would ignore a
host of associated anatomical features in typhlopids not even remotely presaged
in Anomochilus. It therefore seems unlikely that the ectopterygoid of Anomochilus is
structurally transitional between known scolecophidian and alethinophidian
conditions. O n this basis we consider states 1, 2, and 3 each to be unique and
derived.
(23) Pterygoid. Teeth: present ( 0 ) ,absent ( 1 ) . Comment. Polarity follows Estes et
al. (1988).
(24) Pterygoid. Caudal end associated with quadratoarticular joint: closely (0),
distantly (1). Comment. In scolecophidians, the pterygoid extends far caudad to
the quadratoarticular joint, unlike the condition in most other squamates (Haas,
1930a, 1964, 1968; List, 1966).
(25) Quadrate. Proximal end: posterior head of cephalic condyle associated with
stapes (0), no association ofcephalic condyle and stapes (1). Comment. Coding for
this character was derived from Rieppel ( 1 9 8 0 ~ ) .
(26) Quadrate. Proximal articulation: associated with squamosal and
supratemporal (0), associated with supratemporal only ( I ) , associated with otic
elements directly (2). Comment. The dibamid Anelytropszs has a small element
(squamosal or supratemporal according to Greer, 1985; squamosal according to
Estes et al., 1988) between the quadrate and otic elements, although dibamids
are here coded as state 2.
(27) Quadrate. Position of proximal articulation: dorsal, near parietal-prooticsupraoccipital sutures (0), ventral, nearer prootic-basisphenoid-basioccipital
sutures (1).
(28) Maxilla. Association with premaxilla: close, suture or schizarthrosis (0),
close, short ligamentous attachment ( l ) , loose (2). Comment. Mahendra (1938)
used this feature and also designated three states with the same polarity
employed here.
(29) Dentary. Length: greater than 35% of skull (braincase plus snout) length
(0), less than 35% of skull length ( 1 ) .
(30) Coronoid: present and extending dorsal to coronoid process (0), present and
not extending dorsal to coronoid process ( l ) , absent (2). Comment. Kluge (1991)
used a character similar to this with polarity reversed from our usage.
(32) Splenial. Caudal edge: lies anterior to caudal edge of dentary (0), lies
caudal to caudal edge of dentary ( l ) , absent (2).
(32) Compound bone. Retroarticular process: short and unmodified (0), short but
with dorsal spatulate process ( l ) , long (2). Comment. Estes et al. (1988) employed
six features of the retroarticular process, none of which matches any state defined
here.
(33) Stapes: associated with tympanum indirectly through one or more
284
D. CUNDALL ET AL.
intermediate elements (0), associated with posterior tip of cephalic condyle of
quadrate ( l ) , associated with dorsal half of quadrate (2), associated with ventral
half of quadrate (3).
(34) Mandible. Length: 80-100~0 of skull (braincase plus snout) length (0), less
than 80% of skull length ( l ) , more than lOOyo of skull length (2).
(35) Hyoid arch: medial (basihyal) and lateral (hypohyal, ceratohyal, or
epihyal) elements present (0), all lateral elements lost ( l ) , medial and lateral
elements lost (2). Comment. This character refers only to derivatives of the second
visceral arch, and not to the hyoid apparatus as a whole. This character, as well
as characters 37 and 38, was drawn largely from List’s (1966) and McDowell’s
(1967, 1972) analysis of hyoid evolution in snakes and differs from Langebartel’s
(1968) views. McDowell (1967, 1972) suggested that the weight of evidence
favoured first branchial arch origin for the lateral cornua of the anomalepidid
hyoid because the cornua serve as attachment points for the hyoglossi and,
muscles that appear homologous to the omohyoideus and mandibulohyoideus of
other squamates (Warner, 1946). Further, McDowell (1972) supported List’s
(1966) suggestion that the hyoid cornua of all alethinophidians are caudal
extensions of the basihyal. The hyoid of alethinophidian snakes apparently
appears first as a small caudally directed V-shaped element in the midventral
hyoid (2nd visceral) arch. The tips of the V then become elongated rods, the
assumption being that accretion is due entirely to cells associated with the 2nd
visceral arch (Kamal & Hammouda, 1965a, b; Kamal et al., 1970). During
subsequent development, the median basihyal region may be either lost (Eryx
[Kamal & Hammouda, 1965bl and, presumably, all other alethinophidians
with diverging, unjoined cornua) or retained and, in some cases, enlarged by the
addition of an anterior entoglossal process (Kamal & Hammouda, 1965a). This
interpretation has been accepted by Rieppel (1981) and Kluge (1991).
(36) Median basihyal element: present in adult, uniting cornua (0), absent in
adult, cornua separated anteriorly (1). Comment. This character has been used by
Underwood (1976), who noted both states of this feature in pythonids and
bolyeriids, and Kluge (1991), who noted both states of this feature within boines
and used the polarity adopted here. It should be noted that the cornua of all
alethinophidians are here regarded as basihyal derivatives, whether or not a
median structure persists in the adult hyobranchium.
(37) First branchial arch elements: present ( 0 ) , absent, replaced by caudal
extensions of the lateral edge of the basihyal (1).
(38) Pelvic vestiges: present ( 0 ) ,absent (1).
Muscular characters
(39) Adductor mandibulae externus pars superjcialis. Origin: from both braincase and
temporal tendon or arch (0), from braincase only ( l ) , from temporal tendon
only (2). Comment. The homologies of the external mandibular adductors of
snakes have been explored topographically by McDowell ( 1986) and
developmentally by Rieppel (1988~).Both concluded that Lakjer’s ( 1926)
terminology does not reflect the most probable homologies with lacertilian
external adductors. For comparisons among snakes, this poses few problems. In
comparisons that include lizards, however, this creates numerous problems for
which no simple solution is available. In our analysis, the problem is further
ANOMOCHILUS RELATIONSHIPS
285
confounded by the questionable homologies of the external adductors of Dibamus
(Gasc, 1968; Rieppel, 1984). It appears that what has been termed the
superficial external adductor of snakes is homologous, at least in part, to the
levator anguli oris of lizards, and what has been termed the externus profundus of
snakes is, in part, homologous to the externus superjicialis of lizards. Rieppel
(1988c) and McDowell (1986) disagree on homologies of the medialis fibres. In
coding this and succeeding adductor characters except char. 42, we retained the
traditional usage of muscle names for snakes and coded anguimorphs and
dibamids as unknown.
(40) Adductor mandibulae externus pars superjcialis. Insertion: coronoid process or
dorsal edge of surangular plus epimysium of adductor extenus medialis (0), coronoid
process plus dorsal edge of adductor externus profundus ( 1), primarily ventrolateral
surface of compound bone ( 2 ) .
(41) Levator anguli oris: present (0), present with suborbital origin and dentary
insertion ( l ) , absent (2). McDowell (1986 and pers. comm.) regards the muscle
bearing this name in snakes as being absent in lizards and an apomorphy of
snakes, although he questions whether the muscles of this name in different snake
lineages are homologous.
( 4 2 ) Adductor
mandibulae externus pars medialis.
Insertional
tendon
(bodenaponeurosis): prominent (0), reduced or absent ( 1 ) .
( 4 3 ) Adductor mandibulae externus pars profundus. Quadrate tendon: prominent (0),
reduced or absent ( 1 ) .
( 4 4 ) Pterygoideus. Origin: single (0), double, meaning separation of
ectopterygoid and pterygoid origins (1). Comment. The condition of the
pterygoideus in some scolecophidians has superficial similarities to that of
colubroids (Haas, 1973), although the likelihood that the conditions are
homologous seems small. We have coded all scolecophidians as having a single
origin, although there are at least two definable states in this taxon and neither
fits either of the states for alethinophidian snakes.
( 4 5 ) Retractor vomeris: absent (0), present (1).
( 4 6 ) Retractor pterygoidei. Origin: posterolateral to Vidian nerve (0),
anteromedial to Vidian nerve (1). Comment. This character is drawn directly
from McDowell (1987) and appears independent of Rieppel’s (1979b)
interpretation of the evolution of the Vidian canal in snakes.
( 4 7 ) Intermandibularis anterior: undivided and deep (0), undivided and superficial
( l ) , divided (2) (see Groombridge, 1979a).
(48) Intermandibularis anterior. Insertion of pars anterior: none (0), on oral mucosa
and tongue sheath ( l ) , on interramal pad (2). Comment. Coding for this character
is taken directly from Groombridge ( 1979a). The three-state condition arises
from the fact that, in the absence of a divided intenandibularis anterior, there is no
pars anterior.
( 4 9 ) Intermandibularis posterior, pars posterior: present ( 0 ) ,absent ( 1).
( 5 0 ) Omohyoideus: present ( 0 ) , absent (1).
Visceral characters
(51) Tracheal entry into right lung: subterminal to cranial end of lung (0),
terminal, at cranial end of lung (1). Comment. Previously used by Beddard ( 1908,
1909), Thompson ( 1913) and Underwood ( 1967).
286
D.CUNDALL E l AL.
(52) Left lung complex: present (0), absent (1). Comment. Includes the left lung,
left bronchus and left orifice (Cope, 1894).
( 5 3 ) Liver. Posterior extension: absent (0), present ( I ) . Comment. In snakes, the
liver forms left and right lobes lying to either side of the posterior vena cava and
hepatic portal vein. If either lobe extends caudal to its partner by more than 5%
SVL, it is considered to be an extension (Beddard, 1908).
(54) Pancreas. Limb extending to spleen: present (0), absent (1). Comment. As
noted by Underwood (1967), state 1 actually has two expressions, one in which
the pancreas and spleen are completely separated (e.g. some erycines and
boines) and one in which the pancreas and spleen are in broad contact (e.g. all
colubroids) .
(55) Reproductive mode: oviparous (0), viviparous ( I ) . Comment. Although this is
not strictly a visceral character, oviparity is assumed for a number of snake taxa
(e.g. Anomochilus) based solely on the presence of shelled eggs in the oviduct, a
feature which may sometimes be misleading (Blackburn, 1993).
( 5 6 ) Ileocolic caecum: present (0), absent ( I ) . Comment. This character has been
used by McDowell (l974b, 1987).
(57) Eye: cornea covered by eyelids or spectacle (0), cornea lying beneath one
or more head shields ( 1 ) .
(58) Heart. Distance from snout: > 35% SVL (snout-vent length) (0), 26-35%
SVL ( l ) , < 26% SVL (2). Comment. Distance is measured from the snout to the
caudal tip of the ventricle. This and all remaining characters use SVL as the
reference distance measure, following Bergman ( 1953). Intervals for these
continuous characters were selected by grouping values for species included in
each of the scolecophidian and lower alethinophidian families and then looking
for breaks between these groupings. As the sample size for the majority of species
was one, intraspecific variation was unknown and traditional gap coding could
not be used. For each character, data for all species were plotted and the range
of values divided at the two largest gaps.
(59) Right lung. Distance of midpoint from snout: >44% SVL (0),38-44y0 SVL
( l ) , <38% SVL (2). Comment. Wallach (1991) demonstrated that the midpoint
of an organ (previously used by Thorpe, 1975) is the most stable character that
can be derived from the viscera.
(60) Liver. Total length: <24% SVL (0), 2 4 3 2 % SVL ( I ) , >32% SVL ( 2 ) .
Comment. This value incorporates both lobes of the liver.
(61) Liver. Distance of midpoint from snout: >60% SVL (0), 50-60y0 SVL ( l ) ,
< 50% SVL (2).
(62) Liver-gall bladder interval: < -2% (i.e. a greater negative value) SVL (0),
-2 to 7% SVL ( l ) , > 7% SVL (2). Comment. This is measured from the
posterior tip of the liver to the anterior border of the gall bladder. If the anterior
edge of the gall bladder lies cranial to the tip of the liver (as in most lizards in
which the gall bladder is enclosed by or in contact with the liver), a negative
value is obtained (Underwood, 1967).
( 6 3 ) Gall bladder. Distance of midpoint from snout: ~ 6 4 %
SVL (0), 6 6 7 5 %
SVL ( I ) , >75y0 SVL (2).
( 6 4 ) Right kidney. Distance of midpoint from snout: ~ 8 6 %
SVL (0), 86-90y0
SVL ( l ) , >goyo SVL (2).
(65) Left kidney. Distance from caudal edge to vent: > 10% SVL (0), 6-10y0
SVL ( l ) ,
SVL (2).
ANOMOCHILUS RELATIONSHIPS
287
The data were analysed as a whole, as three independent character sets
(skeletal, muscular, visceral) and as three pairs of character sets (skeletalmuscular, skeletal-visceral, muscular-visceral) . All character sets were initially
analysed using one of the branch-swapping algorithms (usually nearest
neighbour or subtree pruning). Strict consensus trees were then constructed for
the trees obtained in the initial analysis. Following this, all characters were
weighted using the rescaled consistency indices from the first analysis, and
another heuristic search was conducted. Relationships between tree topology
and character evolution were examined using MacClade (Maddison &
Maddison, 1992).
RESULTS
Analysing the matrix in Table 2 using either accelerated (ACCTRAN) or
delayed (DELTRAN) transformation and any of the branch swapping
algorithms in PAUP (MULPARS option in effect, multistate taxa treated as
polymorphic) produces four equally parsimonious trees (length 289, CI
[consistency index] = 0.69, HI [homoplasy index] =0.66, R I [retention
index] = 0.68, R C [rescaled consistency index] = 0.47) with a homoplasy slope
ratio (HSR, Meier et al., 1991) of 0.1 1. When characters are weighted using the
maximum value of their rescaled consistency indices, two trees are produced
following a single round of analysis (HSR=0.06; see Table 3 for remaining tree
statistics). The strict consensus of these two trees is given in Fig. 2. O n the basis
of this analysis, Anomochilus is the sister taxon of all alethinophidian snakes.
The form of the tree in Fig. 2 indicates that there are not enough
synapomorphies among the ‘lower’ alethinophidians to unite any of these taxa in
clades more inclusive than their group identity in the original matrix. Because
the characters entered into the analysis were restricted primarily to those
relevant to Anomochilus, relationships drawn among more distantly related clades
were expected to be less reliable, although the general form of the tree
approximates to some previous notions of snake relationships (e.g. McDowell,
1987; Rieppel, 1988a) and Kluge’s ( 1991) preliminary hypothesis of snake
relationships based on 139 characters.
With regard to the placement of Anomochilus, the data set proves to be
reasonably stable in the face of a variety of small changes (exclusions of 1-5
characters). However, of the various subsets of data, only that containing both
skeletal (38 characters) and visceral (15 characters) data yields a tree similar to
that produced by the total evidence. From the consensus trees for skeletal data
alone (Fig. 3 ) or visceral data alone (Fig. 4),however, it can be seen that these
two anatomical systems produce widely differing interpretations of the
phylogeny of snakes and the position of Anomochilus. Muscular characters
produce more than 200 equally parsimonious trees, suggesting that these
characters carry no consistent phylogenetic message. Combining skeletal and
muscular data produces 36 trees that yield a single tree (length 82) following one
round of character weighting. This tree has the form (Anguimorpha,
(Dibamidae,
( ( (Anomalepididae,
Typhlopidae),
Leptotyphlopidae),
( ( ( (Aniliidae, (Cylindrophiinae, (Uropeltinae, Anomochilus) ) ), Loxocemidae),
D. CUNDALL ET AL.
288
TABLE
2. Data matrix for trees in Figs 2-4. Polymorphic states: a = 01, b = 02,c = 12,
d = 23, e = 012, f = 013
Taxon
Angui
Dibam
Anoma
TYPhl
Lepto
Anili
Cylin
Urope
Anomo
Xenop
Loxoc
btho
Boina
Eryci
Bolye
Tropi
Acroc
Colub
Characters
1 2 3
b O O
0 0 1
1 0 0
1
0
0
1
2
2
2
0
2
2
2
0
2
2
2
3
f
0
1
1
1
0
1
1
1
0
1
1
1
0
O
1
0
0
0
0
1
0
1
1
2
1
0
0
O
4
5
6
7
8
9
10 I 1
12 13 14 15 16 17 18 19 20
O
O
O
O
O
O
O
O
a
O
O
O
O
O
a
O
0
0
?
0
0
1
0
0
0
0
0
0
1
0
0
0
O
0
l
1
1
0
1
1
1
0
0
0
l
1
1
1
1
l
a 0
1 0
1 0
0 0
0 0
0 0
0 0
0 0
0 0
0 1
b 1
0 1
2 ?
2 ?
2 1
b 1
0
0
0
1
1
1
1
1
1
1
1
2
1
c
2
2
0
1
1
0
0
2
2
0
0
2
2
2
0
0
0
0
0
1
1
1
0
1
1
1
0
0
0
0
0
0
0
a
0
0
0
0
0
0
0
0
1
1
0
0
0
0
0
O
0
0
0
1
1
1
1
1
1
0
0
0
0
0
0
a
0
0
0
1
1
0
0
1
1
1
1
1
1
1
0
l
0 0
0 0
0 0
0 1
0 1
0 1
0 1
1 1
0 1
1 1
1 1
0 1
0 1
0 1
0 1
a 1
0
0
0
1
1
1
?
0
0
0
0
0
0
0
0
0
0
1
1
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
0
0
0
0
0
0
?
0
0
0
0
0
1
1
0
0
1
1
a
1
1
1
1
1
a
0
0
0
1
1
1
1
1
1
1
1
1
1
I
1
l
0
0
0
1
1
1
1
0
0
2
0
0
0
0
2
b
41 42 43 44 45 46 47 40 49 50 51 52 53 54 55 56 57 58 59 60
Angui
Dibam
Anoma
Typhl
Lepto
Anili
Cylin
Urope
Anomo
Xenop
Loxoc
Pytho
Boina
Eryci
Bolye
Tropi
Acroc
Colub
?
?
0
2
0
0
0
0
0
I
0
2
2
2
2
2
2
b
0
1
1
0
0
0
0
0
0
0
0
1
1
I
1
1
1
1
?
?
I
I
0
0
0
0
0
0
O
1
0
0
0
0
0
0
0
0
1
1
1
I
1
I
0
0
0
0
0
?
0
0
0
0
0
0
1
0
1
0
1
1
O
0
0
1
0
?
?
?
1
0
0
0
0
1
0
0
0
0
0
0
1
1
1
1
0
0
0
1
0
1
0
1
0
0
1
0
1
1
1
1
a
0
0
0
1
a
0
0
I
2
2
2
2
2
2
0
0
0
0
0
0
1
2
2
0
0
0
0
1
0
1
1
0
0
0
a
a
0
0
0
0
0 0 I I
0
0 I 1 a
0
0 I
1
I
0
1 1 0 0
0
I 0 a 0
0
I 0 a a 0 a
1 0 1 1 1 1
I 1 0 0 0 0
I
I 0 0 0 0
I 1 0 0 0 0
1 1 0 0 0 a
I
I O O O a
0 I 1 0 O ?
0 I
1
I 0 I
0 I 1 0 0 0
a I a a a 1
a
0
0
0
0
1
I
I
0
0
0
0
l
l
O
I
I
a
0
0
b
e
?
1
1
1
0
0
1
a
a
0
0
0
0
I
0
0
0
a
0
?
I
1
a
1
1
0
1
a
0
0
0
0
0
0
0
0
O
e
2
I
a
2
2
I
1
2
I
I
a
2
1
I
a
2
0
0
1
I
a
2
I
I
1
0
0
1
I
c
I
0
e
0
a
a
0
0
e
0
0
0
0
0
e
c
e
c
Xenopeltidae),
( ( Pythonidae,
(Boinae,
Erycinae)),
(Bolyeriidae,
(Tropidophiidae, (Acrochordidae, Colubroidea) ) ) ) ) ) )), similar to the consensus
tree for skeletal data alone. Muscular and visceral characters together produce
three trees (length 149) whose consensus has the topology (Anguimorpha,
(( (Anomalepididae,
Typhlopidae),
Leptotyphlopidae) ,
((Dibamidae,
Anomochilus) ) , (Aniliidae, (Cylindrophiinae, Uropeltinae) ) ) , (Xenopeltidae,
(Loxocemidae, (Pythonidae, (Boinae, Erycinae, (Bolyeriidae, (Tropidophiidae,
(Acrochordidae, Colubroidea)) ) ) ) ) ) ) .
Exclusion of characters in which absence was the derived state (chars. 4,9, 16,
ANOMOCHILLJS RELATIONSHIPS
289
TABLE
2. C o d
Taxon Characters
21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
0
0
3
2
2
2
l
1
1
2
1
1
2
1
1
1
0
0
0
3
1
0
O
0
2
0
0
0
0
0
0
0
a
1
1
1
1
0
O
1
1
0
0
0
0
0
0
0
0
0
1
1
1
0
O
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
O
0
0
0
0
1
1
1
1
1
0
2
2
2
2
1
l
2
1
1
1
1
1
1
1
1
0
1
1
1
1
0
O
1
1
0
0
0
0
0
0
0
0
0
2
2
1
1
l
a
1
1
1
2
2
2
2
2
0
0
1
1
1
0
O
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
l
1
1
1
1
1
1
1
1
2
0
2
1
1
0
2
O
0
0
0
0
0
0
0
0
0
0
0
2
2
0
0
O
1
1
0
0
0
0
0
0
0
0 0
3 1
1 1
1 1
1 1
1 0
l O
1 0
1 0
1 0
1 0
2 2
3 2
3 2
2 0
2 2
0 0
0 0
2 1
1 0
1 0
1 0
l O
1 0
1 0
1 0
1 0
1 a
1 a
1 a
1 a
1 0
0 0
0 0
0 a
0 0
0 a
1 0
l O
1 1
1 0
1 1
1 0
1 0
1 0
1 0
1 1
1 a
? ?
? ?
1 0
1 0
1 0
0 1
b l
2 1
1 0
1 2
1 2
1 2
1 2
1 2
1 2
1 2
2
0
0
0
1
1
0
2
0
2
0
0
1
2
1
0
1
1
1
2
d
O
a
0
1
1
0
2
0
2
0
0
d
b
1
0
1
1
1
2
61 62 63 64 65
b O a
0 ? ?
2 1 a
2 l e
2 c l
2 2 . 2
1
l
2
1
0
0
e
2
c
e
c
1
2
e
2
0
0
0
b
2
2
c
l
2
2
l
2
1
0
0
1
I
2
2
2
2
2
l
2
2
2
2
2
2
1
0
0
2
c
2
1
e
c
l
c
1
2
o
l
O
0
e
o
a
a
0
e
o
l
a
0
e
23, 35, 36, 37, 38, 42, 43, 49, 50, 52, 54, 56) gives a consensus tree with a
topology similar to the consensus tree derived from the total evidence. Its major
departures lie in: (1) a basal polytomy uniting anguimorphs, dibamids,
scolecophidians and alethinophidians, (2) a more basal position of bolyeriids
between xenopeltids and pythonids, and (3) the appearance of a clade uniting
aniliids, cylindrophiines and uropeltines. Anomochilus remains the sister group of
all alethinophidian snakes. As can be seen from Table 3, there is no evidence that
the excluded characters contributed a disproportionate share to the total
homoplasy in the data.
290
Anguimorpha
6
Dibamidae
4
3
Leptotyphlopidae
4
3
Anomochilus
5
8
Uropeltinae
2
6
Cylindrophiinae
1
-
Aniliidae
3
4
-
*
4
Xenopeltidae
3
-
Loxocemidae
1
5
2
Pythonidae
4
13
2
4
-
Bolyeriidae
4
1
Tropidophiidae
DISCUSSION AND SYSTEMATIC CONCLUSIONS
Most current classifications of snakes, particularly primitive snakes
(McDowell, 1987; Rage, 1987; Rieppel, 1988a; Kluge, 1991), are drawn
predominately from skeletal features. It is not surprising, therefore, that our
analysis, also based predominantly on skeletal features, produces phylograms
that agree in many respects with these classifications. However, a number of
differences exist between our results and patterns of relationship suggested by
others that pertain directly to our treatment of Anomochilus.
First, the total evidence (Fig. 2) provides little support for the existence of
monophyletic clades corresponding to any previous notions of anilioids or
henophidians. Kluge ( 1991) obtained a clade (Anilius Cylindrophis uropeltines) )
that corresponded closely to Rieppel’s (1988a) conception of anilioids and
++
AXOMOCHILUS RELATIONSHIPS
I
29 1
Anguimorpha
1
Dibamidae
Leptotyphlopidae
Anomalepididae
2
r E
1
Typhlopidae
Xenopeltidae
Loxocemidae
Aniliidae
Cylindrophiinae
I---
Uropeltinae
Anomochilus
I
2
l7-m-
I
4
Pythonidae
Boinae
L E2r y c i n a e
Bolyeriidae
Tropidophiidae
17
Acrochordidae
Colubroidea
Figure 3. Strict consensus of four trees derived from skeletal characters (characters 1-38) alone.
Numbers below branches as for Fig. 2.
’
differed from McDowell’s ( 1975, 1987) arrangements in excluding xenopeltids
and loxocemids. Older, more inclusive arrangements (Booidea of Romer, 1956;
Henophidia of Underwood, 1967) obtain even less support from the total
evidence. For primitive alethinophidians
(Anomochilus, Uropeltinae,
Cylindrophiinae, Aniliidae, Xenopeltidae, Loxocemidae), our analysis of the
total evidence provides no resolution of categories higher than the terminal taxa.
O n the other hand, the total evidence does support the fundamental division of
snakes into scolecophidian and alethinophidian clades, contrary to relationships
suggested by Dowling (in Dowling & Duellman, 1978; reaffirmed in a privately
distributed work and by Dowling, 1988).
Within the framework of total evidence, our data also provide little support
for a monophyletic ‘uropeltid’ Asian clade that includes Anomochilus and
Cylindrophis as suggested by Romer ( 1956; subfamily Uropeltinae of his family
292
Dibamidae
3
Anomalepididae
1
1
4
0
Typhlopidae
Leptotyphlopidae
2
-Anomochilus
1
1
Boinae
0
Erycinae
0
1
Loxocemidae
1
1
-
0
3
Pythonidae
Acrochordidae
Aniliidae) and McDowell (1975, 1987). Instead, the total evidence supports
previous observations of the paucity of synapomorphies uniting these clades
(Rieppel, 1988a) and the relatively greater distances separating Cylindrophis
(including the Sri Lankan C. maculatus) from all ‘uropeltine’ genera, as suggested
by the data of Dessauer et al. 1987) and Cadle et al. (1990). However, among the
taxa examined, their analysis showed Cylindrophis to be the sister group of
uropeltines) . As noted previously, Anomochilus has uniformly been allied to
Cylindrophis rather than uropeltines. Rieppel’s ( 1977a) original suggestion of the
wide separation of Anilius from Cylindrophis has been supported by molecular
studies (Dessauer et al., 1987; Cadle et al., 1990), but the placement of these two
taxa relative to other primitive snakes has remained equivocal. Our results
suggest that Anilius and Cylindrophis, despite superficial resemblances to Dinilysiu
(Estes el al., 1970), may not be the most plesiomorphic living alethinophidians.
AN0 MOCHILUS RELATIONSHIPS
293
TABLE
3. Tree statistics for PAUP analyses of different character sets from Table 2. Statistics for
the original search (SPR branch swapping) and for a second search following weighting of
characters to rescaled consistency indices from first search. T L = tree length, Tf = number of
trees generated, CI = consistency index, HI = homplasy index, RI = retention index, RC =
rescaled consistency index, No Abs = character set excluding characters in which absence was the
derived state, Total Ev = complete data matrix
Original Search
1 Round Char. Weighting
Set
TL
T#
CI
HI
RI
RC
TL
T#
CI
HI
RI
RC
Skel
132
31
Ill
168
253
149
226
289
23
292
56
36
0.64
0.71
0.84
0.64
0.70
0.77
0.73
0.69
0.56
0.45
0.79
0.55
0.68
0.73
0.64
0.66
0.70
0.85
0.71
0.72
0.66
0.71
0.71
0.68
0.45
0.60
0.59
0.46
0.46
0.55
0.52
0.47
63
21
78
82
113
81
155
130
4
216
7
0.76
0.80
0.88
0.75
0.83
0.86
0.79
0.81
0.49
0.38
0.80
0.46
0.64
0.70
0.61
0.61
0.82
0.89
0.76
0.82
0.81
0.83
0.80
0.82
0.62
0.71
0.66
0.62
0.67
0.71
0.63
0.66
Musc
Visc
Sk Mu
Sk+Vi
Mu+Vi
No Abs
Total Ev
+
1
3
12
4
I
1
6
2
2
Figure 2 presents the hypothesis that the most primitive living alethinophidian
snakes are the specialized, rather than the generalized, fossorial snakes.
However, skeletal data alone (Fig. 3) and skeletal plus muscular data both
yield trees in which the alethinophidians are split into two major clades, one
corresponding to McDowell’s ( 1987) Anilioidea (aniliids, cylindrophiines,
uropeltines, Anomochilus, loxocemids and xenopeltids) and one containing the
remaining lineages. In both analyses Anomochilus is the sister taxon of uropeltines.
The fact that this division of the alethinophidia collapses with the addition of
more evidence should not obscure the fact that many past conceptions of snake
relationships, overwhelmingly drawn from skeletal characters, are indeed
supported by our skeletal characters as well.
Soft anatomical characters have been used more widely since Underwood
(1967) reaffirmed their utility, but most recent uses have concentrated on
visceral variations within species (e.g. Thorpe, 1975, 1979, 1984; Wuster &
Thorpe, 1989, 1990) or among closely related species (e.g. Rasmussen, 1986,
1989a, b; Wallach, 1985, 1988, 1991). Interpretation of these characters at the
level at which we have employed them remains more problematic. Accepting the
results of our analyses of muscular and visceral characters would require, among
other things, abandoning current definitions of the Alethinophidia and
Scolecophidia and reassessing the relationships of dibamids to snakes and lizards.
This seems premature. On the basis of all soft anatomical characters Anomochilus
lies at the base of a scolecophidian clade (Anomochilus (Leptotyphlopidae
(Anomalepididae,Typhlopidae) ) ) that is a sister taxon of dibamids. In this
arrangement, snakes are polyphyletic, as they would be also on the basis of
visceral data alone (Fig. 4). However, Dowling’s ( 1978-in
Dowling and
Duellman, 1978; 1988) suggestions that ‘uropeltines’ are most closely related to
leptotyphlopids and that Anomochilds and Cylindrophis are sister taxa of a boineerycine clade are not supported by any of our data.
Acceptance of the tree in Fig. 2 requires revision of a number of assumptions
about primitive snakes entailed in most recent systematic arrangements. First,
there is no suprafamilial clade corresponding to either McDowell’s (1987) or
Rieppel’s ( 1988a) Anilioidea. Second, inclusion of Anomochilus and Cylindrophis in
294
D. CUNDALL ET AL.
the Uropeltidae makes that family paraphyletic in our hypothesis of
relationships. Third, the most primitive living alethinophidians may be
specialized fossorial snakes, lending support for Walls’ ( 1942) original contention
of a fossorial ancestry for all snakes, and further suggesting that Cylindrophis and
Anilius may be living relicts of early divergent experiments in increased body size,
a less fossorial existence, and attendant changes in feeding ecology and
mechanics.
O n the basis of its Sunda Shelf distribution, Anomochilus lies within the ranges
of cylindrophiines and typhlopids. However, it lies well outside the current range
of uropeltines, the clade with which it seems most closely allied from skeletal data
(Fig. 3). Living primitive snakes all appear to occupy relict distributions (Cadle,
1987), regardless of which particular hypothesis of phylogeny one chooses. Fossil
data provide no clues because there are no uropeltine fossils (Rage, 1987).
Therefore, there are no current data independent of anatomy upon which to
evaluate the phylogenetic relationships of Anomochilus.
Our interpretation of the relationships of Anomochilus to other snakes adheres
strongly to the tree derived from the total evidence. Because the characters we
used emphasize features relevant to lower alethinophidians and scolecophidians,
the absence of synapomorphies uniting these taxa into groups more inclusive
than those shown in Fig. 2 confirms a long-standing problem in assessing
phylogenetic relationships among these taxa. To most accurately reflect our
findings, we suggest that Anomochilus be regarded as the sister taxon of all other
Alethinophidia. Its current inclusion in the family Uropeltidae makes that
family paraphyletic in our hypothesis of relationships and we therefore create a
new monotypic family, Anomochilidae, to contain the genus Anomochilus.
Acceptance of the tree in Fig. 2 also requires that Cylindrophis be removed from
Uropeltidae for the same reason. We resurrect Fitzinger’s (1843) family
Cylindrophes as Cylindrophiidae, restricting its content to Cylindrophis and the
Eocene fossil Eoanilius.
Anomochilidae, fam. nov.
Diagnosis. Small ( <400 mm total length), cylindrical-bodied snakes with head
no wider than body; no mental groove; four supralabials, third in contact with
eye; loreal absent; scales smooth in 17-19 rows; anal divided; subcaudals single;
eye reduced; spectacle reduced or absent; ventrals scarcely wider than first dorsal
scale row; pelvic vestiges present; teeth absent on premaxilla, palatine and
pterygoid; maxillary teeth three or four; dentary and maxillary teeth short with
stout bases; ectopterygoid reduced to a small splint embedded in pterygomaxillary ligament; occipital condyle sessile (the last two features known only
from radiographs for A . leonardi); left lung and tracheal lung absent; two renal
arteries; no rectal caecum. The following features are known only for one
specimen of A . weberi: premaxillary nasal process short and not extending
between nasals; septomaxilla with anterohedial process extending dorsally
toward nasal; choanal process of palatine complexly articulated with caudal
edge of vomer; supratemporal present; coronoid present and forming tip of welldeveloped coronoid process; hyoid V-type with wide anterior separation of
cornua; cutaneous muscles begin just caudal to postorbital ligament and cover
lateral mandibular adductors; levator anguli oris present; posterior (temporal
AN0 M OCHILUS R ELATIONSH I PS
295
tendon) head of adductor externus superjicialis absent; retractor vomeris and
protractor quadrati absent; omohyoideus present.
Content. Anomochilus Berg, 1901 (substitute name for Anomalochilus Lidth de
Jeude, 1890).
Distribution. Indonesia (west-central Sumatra and eastern Kalimantan) and
central Malay Peninsula (Pahang, Selangor) of Malaysia.
Cylindrophiidae Fitzinger, 1843
Diagnosis. As for Anomochilidae except: small to moderate in size (some
species exceeding 750 mm total length); prominent mental groove; six
supralabials, third and fourth entering eye; scales smooth in 19-23 rows; teeth
present on palatine and pterygoid; maxillary teeth 9- 13; ectopterygoid robust
and extensively overlapping maxilla and pterygoid; premaxillary nasal process
long and extending between nasals; vestigial left lung present; posterior head of
adductor externus superjicialis present.
Content. Cylindrophis Wagler, 1828; (3) Eoanilius Rage, 1974. Distribution of
living species: Sri Lanka, Myanmar, Thailand, Kampuchea, Vietnam,
Malaysia, Singapore, and Indonesia.
Comment. McDowell ( 1987) included the fossil species Eoanilius europae from the
Upper Eocene of France and England in his subfamily Cylindrophiinae on the
basis of geographic distribution. We regard this placement as questionable
because available geological, geographical and morphological data seem to
provide no more reason to assign Eoanilius to Cylindrophiidae than to Aniliidae.
ACKNOWLEDGEMENTS
This study would not have been possible without the cooperation of M.
Hoogmoed, Rijksmuseum van Natuurlijke Historie, who permitted dissection of
one specimen of A . weberi. This provided the anatomical foundation for most of
the characters used in our study. Critical supporting data were obtained from
radiographs provided by S. Taylor and R. Pechman, Veterinary Teaching
Hospital and Clinic at Louisiana State University. Additional comparative
information was gained from examination of many museum specimens made
possible by the kind cooperation of E. V. Malnate, Academy of Natural Sciences
of Philadelphia, R. G. Zweifel and C. W. Myers, American Museum of Natural
History; E. N. Arnold, C. J. McCarthy and A. F. Stimson, British Museum
(Natural History); A. E. Leviton and R. C. Drewes, California Academy of
Sciences; R. F. Inger, H. Marx, and H. Voris, Field Museum of Natural History,
Chicago; P. Alberch, J. P. Rosado and E. E. Williams, Museum of Comparative
Zoology, Harvard; L. Maxson, University of Illinois Museum of Natural
History; W. E. Duellman, University of Kansas Museum of Natural History;
A. G. Kluge, University of Michigan Museum of Zoology; G. K. Pregill, San
Diego Society of Natural History; R. E. Etheridge, San Diego State University;
P. E. Vanzolini, Museo de Zoologia, Universidad de S2o Paulo; T. D. Schwaner,
South Australia Museum; J. R. Dixon, Texas A. & M. University; and K.-S.
Chifundera, Institut de Recherches Scientifique, Bukavu, Zaire. K. Brown-Wing
did the drawings of the head of A . weberi. We thank J. E. Cadle, H. W. Greene,
F. J. Irish, A. G. Kluge, S. B. McDowell, and A. H. Savitzky for their critical
D. CUNDALL E T AL.
296
and thoughtful reviews of the manuscript. Financial support for this work was
provided in part by Lehigh University faculty research grants to DC.
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