Order Squamata- Suborder Serpentes
Snake Characteristics
Morphology
• Limbless – no pectoral girdle or
forelimbs; pelvic girdle and
hindlimbs rudimentary if
present
• Elongated body
• Glottis – breathe while
consuming prey
• No scleral ossicles to support
eye
• Transparent spectacle covering
eye
• No tympanum
• 120+ precloacal vertebrae (to
upwards of 400!)
Snake Characteristics
Skin
• Skin covered in scales
(have a keratinous
outer layer)
• Outer layers of
epidermis are shed at
one time
• May be elongate,
overlapping, or
keeled or
combination
• Eyes milk over before
shedding (1st sign)
DORSAL VIEW
VENTRAL VIEW
Skin
Skin
Snake Characteristics
Reproduction
• Pair of copulatory organs – hemipenes (used one at a time)
• Oviparous, viviparous
(2 different types of “viviparity”)
• Genetic sex determination
Snake Characteristics
Feeding
• Highest degree of cranial kinesis of any tetrapods
• Most snakes have unilateral feeding (right and left bones
of upper jaw move alternately)
• Most swallow prey whole
• Methods of killing prey:
• Constriction
• Immobilizing prey with
fangs, starting digestion
• Non-venomous snakes
• Duvernov’s gland (rear-fang)
• Venemous glands (front-fang)
Dentition
• Aglyph
• Opistoglyph
• In non-venomous
colubrids, many
constrictors
• In venomous
colubrids (rearfanged: associated
with Duvernoy’s
gland)
• Proteroglyph
• In elapids (long
maxilla, short fangs,
small venom gland)
• Solenoglyph
• In viperids (reduced
maxilla, long fang,
large venom gland,
moveable) Video
Venoms
• Complex mixtures of proteins and other molecules (derived
from digestive enzymes)
• In opistoglyph snakes- associated with Duvernoy’s gland (Colubrids)
• In other snakes- associated with derived venom glands
(large, grooved posterior maxillary teeth)
• Viperid venoms – generally hemolytic (attacks blood
and cytolytic (destructs cells) : Video
internal bleeding)
• Elapid venoms – generally neurotoxic (immobilizes prey, permanent
damage, suffocates 1st)
Pit Organs
• Sensory structures sensitive infrared receptors
• Obtains spatial information about thermal environments
transferred to brain as a visual image
• Pit vipers: between nostril and eye
• Many boas and pythons: paired structures along lips
Copperhead (Viperidae)
Ball python (Boidae)
Infraorder Scolecophidia:
Primitive snakes- solid skulls
• Degenerate, vestigial
eyes; lie beneath opaque
head scales
• Retina only contains
rods – primitive eyes
• Small with blunt heads,
many species have
spiked tails (most <30
cm, largest recorded at
100 cm)
• Fossorial
• All oviparous
Family Typhlopidae:
Cosmopolitan blind snakes
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>252 species
Tropics worldwide
Shovel-like rostral shield
Teeth on upper jaw
Feed via maxillary raking
Family Leptotyphlopidae:
Thread snakes, slender blind snakes
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116 species
S. and Central America, SW US, Africa, Middle East
Many species have well developed pelvic girdles and femurs
Teeth on lower jaw, feed via mandibular raking
Symbiotic relationship with screech owls (Leptotyphlops dulcis)
Other Families:
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Anomalepididae – Dawn blind
snakes (Central & S.America):
teeth on upper and lower jaws,
greatest # of scale rows
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Xenotyphlopidae – Malagasy
blind snakes (Madagascar, 2
species): enlarged, circular
rostral shield
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Gerrhopilidae – Blind snakes
(India, 15 species): extensive
glandular structures in head
scales
Infraorder Alethinophidia:
“More advanced” snakes- kinetic skulls
• Henophidians- relatively primitive group
• Caenophidians- advanced snakes
Family Tropidophiidae:
Dwarf boas
• 2 genera, 34 species
• Nonvenomous
constrictors
• Left lung absent
• Viviparous (true
viviparity)
• W. Indies and tropical S.
and Central America
• Spontaneous
hemorrhaging behavior
• Up to 1m in length
Family Pythonidae:
Pythons
• 40 species, sub-Saharan Africa,
South and SE Asia to Australia
• Nonvenomous* constrictors
• Size range from 35 cm to 10 m!
• Range of habitats: desert to rain
forest
• Cloacal spurs present
• Oviparous (females wrap
around eggs , use muscular
contractions) to incubate
• Have pit organs
• Contain the longest extant snake
(Malayophyton reticulatus) at 9 m!
Case study: Burmese Pythons in FL
• Introduced to Everglades,
invasive
• An estimated 30k-300k pythons
could be in the Park
• Since 2002, over 1,300 pythons
removed (367 in 2009, 246+ in
2010)
• Clutch size: 29-50 eggs 
prolific
• Implicated in significant
declines of native mammalian
species
• Models predict pythons capable
of expanding north as far as
New Jersey
Family Xenopeltidae:
Sunbeam snakes
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2 species; up to 1.3 m in length
Southeastern Asia
Nonvenomous constrictors
Lowland habitats; burrowers
Nocturnal, oviparous
Iridescent smooth, shiny scales
Family Uropeltidae:
Shield-tail snakes, pipe snakes, and dwarf pipe snakes
• 8 general, 54 species; up to
80 cm length
• Sri Lanka, southern India,
SE Asia
• Highly specialized
burrowers
• Viviparous
• Conical heads (usually with
keratinous tip)
• Blunt tails with enlarged,
rough scale at end (shield)
• Nonvenomous, diet mostly
invertebrates
Family Boidae:
Boas
• 3 subfamilies:
-Boinae (34 species),
-Ungaliophiinae (3 species),
-Eyrcinae (14 species)
• Western N. America to S. America,
West Indies, Central Africa, S.
Asia, Madagascar, SW Pacific
Islands
• Nonvenomous, viviparous
• Vestigial pelvic girdle, cloacal
spurs
• Heaviest extant snake (Eunectus
murinus), the green anaconda up
to 91 kg
Family Boidae:
Boas
• Boinae: 60 cm – ??
Terrestrial or aquatic
– Labial pits
• Ungaliophinae: <76 cm
– Rocky terrain
• Erycinae: <70 cm
– Arid or semiarid
– No pits
“Titanoboa” now in Morrill Hall, Nebraska State U
Family Bolyeriidae:
Mascarene or split-jaw snakes
• 2 species
• Mauritius and northern
islets
• Nonvenomous
constrictors
• 2 species oviparous, 3rd
unknown
• Hinged maxilla
adapted to gripping
slippery geckos and
skinks
Family Acrochordidae:
Wart snakes or file snakes
• 3 species; up to 2.5 m length
• S and SE Asia down to
Australia
• Small head, thick-body with
baggy skin (strongly keeled)
• Some cutaneous respiration
• Highly aquatic; nocturnal;
viviparous
• Possible parthenogenesis
• Coastal rivers, estuaries,
marine habitats
Family Viperidae:
Vipers and pit vipers
3 subfamilies, 328 species:
Crotalinae (pit vipers)
-(facial pits)
Viperinae (vipers)
Azemiopinae
- 2 species (Azemiops spp.)
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Venomous snakes
Viviparous or oviparous;
Parental care in Crotalinae
Terrestrial and arboreal
Agkistrodon contortrix:
Copperhead
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Large (60-90 cm), no rattle
Weakly keeled scales
Coppery red, wide head
Dark cross bands in
hourglass pattern down
back
• Open areas of deciduous
forests
• Viviparous; mostly
nocturnal
Agkistrodon contortrix:
Copperhead
Crotalus horridus:
Timber rattlesnake
• Largest venomous snake in
NYS (189 cm record, generally
90-152cm)
• Strongly keeled scales; wide
head; rattle
• Numerous small scales on
head
• Yellow and dark morphs
• Deciduous mountain forests
• Viviparous
• Late maturing, reproduce
every 3-4 years
• Hollow structures made of keratin; make loud sound when
rubbed together as snake vibrates its tail
• New rattle when snake sheds (but old ones can rub off)
Crotalus horridus:
Timber rattlesnake
STATUS:
THREATENED
Threats
• Collection and
killing
• Development
• (Low reproductive
rate)
Sistrurus catenatus:
Massasauga
• Medium-sized and venomous;
rattle
• Keeled scales; large scales on head
• Gray to light brown with multiple
rows of dark blotches
• Narrower head than rattlesnakes,
smaller
• Wetland-dependent
• Viviparous
• Massasauga—derived from
Chippewa term for wetland (“great
river mouth”)
Sistrurus catenatus:
Massasauga
STATUS:
ENDANDERED
Threats
• Natural succession
(Cicero)
• Wetland drainage
• Habitat fragmentation
• Over-collection and
killing
Family Homalopsidae:
Asian water snakes
• 28 genera, 53 species,
• S and SE Asia
• 20 cm-1.4 m TL
• Distinguished from colubrids
by valvular, crescentic nostrils,
dorsally oriented eyes
• Nocturnal, aquatic
• Mostly nonvenomous, some
rear fanged venomous species
Family Elapidae:
Cobras, coral snakes, mambas, kraits, sea snakes, and allies
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353 species (some marine); all venomous
World’s deadliest snakes; proteroglyph dentition
Most are terrestrial species; oviparous
One-to-one correspondence of ventral scale with
the vertebrae
• Neurotoxin paralysis in prey
Micrurus sp. – coral snake
Common Krait Bungarus caeruleus
Family Elapidae:
Cobras, coral snakes, mambas, kraits, sea snakes, and allies
• Some cobras build nests and guard
them (e.g., king cobra)
• Longest venomous snakes: king cobra,
black mamba
King cobra –
Ophiophagus hannah
Black mamba –
Dendroaspis polylepis
Taipan - Oxyuranus scutellatus
Elapidae:
Sea snakes and sea kraits
• 14 genera: All marine species viviparous [except
Laticauda (kraits)- oviparous, goes to shore to lay
eggs]
• Found in coastal marine, estuarine waters and coral
reefs; feed on fish and fish eggs
Family Colubridae:
Common snakes
• Largest snake family
(~1,800 species)
• Terrestrial, aquatic, or
fossorial
• Oviparous or
viviparous
• Some venomous; most
harmless
Nerodia sipedon: Northern water snake
• Fairly large (60-140 cm);
most aquatic NY snake
• Strongly keeled scales
• Dark with brown, red, or
grayish cross-bands
• Permanent freshwater
habitats
• Viviparous; diurnal in
spring and fall, nocturnal
in summer
Nerodia sipedon
Agkistrodon contortrix
Nerodia sipedon:
Northern water snake
Regina septemvittata:
Queen snake
• Small (<60 cm); likely rarest
NY snake
• Keeled scales, ventral stripes
• Dark tan-black with yellow
stripe on lower sides (may fade
in older individuals)
• Moving water with nearby
shrubs
• Specialize on recently molted
crayfish
• Viviparous
Regina septemvittata:
Queen snake
STATUS:
ENDANDERED
Threats
• Declining crayfish
populations
• Siltation/ pollution
(insecticides)
Storeria dekayi:
DeKay’s brown snake
• Small (largest specimens 49 cm);
keeled scales
• Brown or gray with 2 rows of black
dots running down back
• Most terrestrial and marshy
habitats; highly abundant; mostly
nocturnal
• Viviparous
Storeria dekayi:
DeKay’s brown snake
Storeria occipitomaculata:
Red-bellied snake
• Smallest snake in NYS (<30cm)
• 2 color morphs; red/brown back
and gray back; red belly
• May have 4 narrow black
stripes and faint light stripe on
back
• 3 light spots behind head
• Primarily moist forests; can be
in suburbs
• Diurnal in spring and fall;
mostly nocturnal in summer
• Viviparous
Storeria occipitomaculata:
Red-bellied snake
Thamnophis brachystoma:
Short-headed garter snake
• Small (shorter than common)
• Keeled scales
• Brown with 3 light stripes, no spots
between stripes, narrow head
• Meadows, forest edges
• Viviparous
Thamnophis brachystoma:
Short-headed garter snake
Thamnophis sauritus:
Eastern ribbon snake
• Medium-sized and slender
• Keeled scales
• 3 light stripes on dark
background; small spot of
yellow in front of eye
(unlike queen snake)
• Very long tail
• Pond, marshes, swampsfairly aquatic but bask in
grass
• Viviparous
Queen snake
Ribbon snake
Thamnophis sauritus:
Eastern ribbon snake
Thamnophis sirtalis:
Common garter snake
• Small to medium-sized; Most
widespread snake in NY
• Keeled scales
• Most variable in color,
usually 3 light stripes (spots
may occur between stripes)
• Habitat generalists
• Viviparous (true viviparity)
Thamnophis sirtalis:
Common garter snake
Liochlorophis (Opheodrys) vernalis:
Smooth green snake
• Small and slender;
smooth scales
• Bright green with white
belly; long tail
• Wet grassy areas near
forests, lakes, wetlands
• Oviparous; short
incubation period
• Taxonomy still
unresolved, depends on
which source you’re
looking at
Liochlorophis (Opheodrys) vernalis:
Smooth green snake
Carphophis amoenus:
Eastern worm snake
• Small; smooth, glossy scales
• Brown with pink belly; small
head and eyes; blunt tail
• Moist forests near streams;
mostly fossorial
• Oviparous
Carphophis amoenus:
Eastern worm snake
STATUS:
SPECIAL
CONCERN
Major Threat
• Development of
habitats
Coluber constrictor:
Eastern racer
• Large and slender; smooth,
glossy scales
• Black with white chin and
dark belly
• Young racers strongly
patterned
• Does not constrict!
• Open woodlands, shrub
grasslands
• Oviparous
Coluber constrictor:
Eastern racer
Diadophis punctatus:
Ring-necked snake
• Small and slender; smooth
scales
• Bluish-gray back with
yellow/orange belly and
neck ring
• Forest openings/ edges;
mostly nocturnal
• Oviparous
Diadophis punctatus:
Ring-necked snake
Elaphe (Pantherophis) alleghaniensis:
Eastern rat snake
• Longest snake in NY; keeled
scales, esp. along vertebrates
• Black with white checkered belly
(young = patterned); white chin
and throat
• Does constrict!!
• Woodlands and woodland edges
• Oviparous
Elaphe (Pantherophis) alleghaniensis:
Eastern rat snake
Heterodon platirhinos:
Eastern hognose snake
• Medium-sized and thick;
keeled scales
• Typically lighter
background with dark
blotches & light belly;
flattened, upturned
snout
• Forests, fields; sandy
soils
• Oviparous
• Many defensive
behaviors (biting as last
resort) Video
Heterodon platirhinos:
Eastern hognose snake
STATUS:
SPECIAL
CONCERN
Threats
• Habitat loss
• Killing
• Road mortality
Lampropeltis Triangulum:
Milk snake
• Medium-sized; smooth, shiny
scales
• Red or reddish-brown blotches
with black outline; checkerboard
belly
• Old fields, farmland, field edges;
mostly nocturnal
• Oviparous
Lampropeltis Triangulum:
Milk snake
Your turn!
Carphophis amoenus
Eastern worm snake
Diadophis punctatus
Ring-necked snake
Agkistrodon contortrix
Copperhead
Lampropeltis triangulum
Milk snake
Thamnophis sauritus
Eastern ribbon snake
Elaphe alleghaniensis
Eastern rat snake
On to the specimens…