Herpetology Practical 2

Snakes, Squamata skull evo, Tuataras/Rhynchocephalia, Turtles & Crocs, FoCo Native Species

Snakes are in which order?

Order Squamata

Families: 25 total, 7 for us to know

Snake Families

Colubridae
Viperidae
Leptotyphlopidae
Elapidae
Pythonidae
Loxocemidae
Boidae

Snake Distribution & Hotspot

Distribution: Global (except Antartica)
Hotspot: Mexico

Snake Family Phylogenetic Tree

Families with the most species

• Colubridae – 2,055

• Elapidae – 389

• Viperidae - 341

Families with only one species

• Aniliidae

• Loxocemidae

• Xenotyphlopidae

Body Scale Type

Keeled/Rough or Smooth

Anal Scale Type

Single or Divided

Labial Scales

Barred or Plain

Head Scales

Large plate scales or Many small scales

Supraocular or absentt

Rostral scale

Head Shapes

Angular, Wide, Blunt/round, Flat, Rectangular, Wedge, Large

Eye morphology

Body type

body size, tail length, rattle present or not

Rattle

Patterns

Banded, Striped, Saddle, Mask, Ring neck, Dark or Black neck patterns, Checkered

Reproductive Strategy

Colorado Families Snakes

Colubridae - most snakes

Leptotyphlopidae - blind snakes

Viperidae - vipers, ratlesnakes

Colubridae - 70% of all snakes

Morphological diverse family

• distinct labial scales

• large plate head scales

• Wide ventral scales

CO Genera

1. Thamnophis

2. Lampropeltis

3. Coluber

4. Arizona

5. Diadophis

6. Heterodon

7. Hypsiglena

8. Opheodrys

9. Nerodia

10. Pantherophis

11. Pituophis

12. Rhinocheilus

13. Sonora

14. Tantilla

15. Tropidoclonion

Genus: Thamnophis

CO species (5): T. elegans, T. cyrtopsis, T. sirtalis, T. radix, T. proximus

• distinct supraocular scale, large eyes w/ round pupils, large labial scales,

• rectangular head, blunt rostrum

• usually single anal scale, keeled scales

Genus: Lampropeltis

CO species (2): L. getula, L. triangulum

• round head, large plate head scales

• smooth + glossy scales, banded color pattern

• usually single anal scale

Genus: Coluber

CO species (3): C. constrictor, C. flagellum, C. taeniatus

• angular head, distinct supraocular scale, large head plates, long tail and body

• anal scale divided

• many have smooth scales & some keeled

• distinct supraocular, broad labial scales

• long braid like tail

Genus: Arizona

CO species (1): A. elegans

• large head plates, mask on face, labial scales

• smooth + glossy scales, saddle pattern

• single anal scale

Genus: Diadophis

CO species (1): D. punctatus

• flat head, large head scales

• ring neck color pattern

• small bodies, smooth scales, divided anal scale

Genus: Heterodon

CO species (1): H. nasicus

• keeled scales, saddle color pattern

• divided anal scale

• upturned rostral scale, blunt & wide head, mask on head

will play dead

Genus: Hypsiglena

CO species (1): H. torquata

• flat & angular head, large head plate scales, elliptical pupils

• checkered dorsal pattern, dark neck & nape patch

• mask on face, divided anal scale, smooth scales

Genus: Opheodrys

CO species (1): O. vernalis

• large head plate scales, angular head, distinct supraocular scales

• slender body, large eyes, smooth scales, divided anal scale

Genus: Nerodia

CO species (1): N. sipedon

• Large head, barred labial scales

• saddle pattern, rough keeled scales, large-xbodied, divided anal scale

Genus: Pantherophis

CO species (1): P. emoryi

• angular head, mask on face, labial scales

• saddle color pattern, smooth scales, long body

• divided anal scale

Genus: Pituophis

CO species (1): P. catenifer

• Large bodied, saddle color pattern, keeled scales, single anal scale

• large head & head plate scales, distinct rostral scale, barred labial scales

can widen head when pretending to be rattlesnake (even shakes its tail)

Genus: Rhinocheilus

CO species (1): R. lecontei

• angular head, distinct rostral scale, barred labial scales, round pupils

• banded color pattern, smooth scales, single anal scales

Genus: Sonora

CO species (1): S. semiannulata

• blunt & angular head, large-headed plate scales

• small body, saddle or banded color pattern, smooth scales, divided anal scale

Genus: Tantilla

CO species (2): T. nigriceps, T. hobartsmithi

• flat head, rounded rostrum, large head plate scales, black head

• smooth scales, small body, light body, divided anal scale, small size

Genus: Tropidoclonion

CO species (1): T. lineatum

• keeled scales, small size, single anal scale

• blunt/rounded head, 5-6 labial scales

• distinct ventral pattern, distinct dorsal stripe

Viperidae - Vipers & Rattlesnakes

• Wide head

• Many small head scales

• Distinct supraocular scale

• Keeled scales

• Sensory pits

• Most elliptical pupils

• Rattle

CO Genera

1. Crotalus

2. Sisturus

Genus: Crotalus

CO species(2): C. viridis & C. oreganus

• short wide body, short tail, large rattle

• wide head with many small scales

• rough-keeled scales

• elliptical pupils, mask on face

• saddle color pattern

Genus: Sisturus

CO species(1): S. catenatus

• small body, small rattle, short tail

• large plate head scales, wide head, distinct mask

• rough keeled scales

• saddle color pattern

• divided anal scale

Leptotyphlopidae - Thread snakes

• tiny snakes, vestigular eyes

• small rounded, blunt head

• mandibular (jaw) is inset (overbite)

CO Genera

1. Leptotyphlops

Genus: Leptotyphlops

CO species (1): L. dulcis

• smooth shiny scales, small body size (length 10-30cm)

• vestigial eyes, inset lower jaw, round blunt head, no teeth on upper jaw

• some large head plates

• single anal scale

Elapidae - Cobras, Adders, Mambas, etc.

• Venomous, fixed hollow fangs

• angular head, large labial scales

• most have smooth scales

• most have slender bodies, wide range of sizes

Pythonidae - Pythons

• have premaxilla, rectangular head & snout, distinct labial scales (often with pits)

• large-bodied, smooth scales, many large plate scales b/w eyes

• vestigial limbs

Loxocemidae - Mexican burrowing snake

1 species in this family

• shovel-shaped snout, angular head, small eyes

• iridescent small smooth scales on body

• large head plate scales

• pelvic spurs (vestigial limbs)

Boidae - Boas

• many have rectangular head, others rounded blunt heads

• many small scales b/w eyes

• wide bodies, short tails, smooth scales, vestigial limbs (pelvic spurs)

Turtle Phylogeny

Turtle Distribution & Hotspots

Distribution: Equatorial

Hotspots: New Guinea, Amazon, Congo

Turtle Head retraction

Cryptodira: striaght

Pleurodira: sideways

Tubercles

Spikes on the dorsal aspect of the neck

Nose shapes

snorkel, beak, or normal

Head size

large vs small

Carapace

Flat vs Domed

Smooth vs Ridged

Scute & Plastron

Scute: Patterns on carapce

Plastron: Shape and pattern (ventral)

Feet

Degree of webbing/claw shape or Paddles

Tail

size and shape

Colorado Turtle Families

Chelydridae - Snapping turtles

Emydidae - Box & Pond turtles

Kinosternidae - Mud & Musk turtles

Trionychidae - Softshell turtles

Chelydridae - Snapping Turtles

• Large heads and limbs that can’t retract into shell

• hooked upper jaw

• long tails

• tubercles on head & neck

• ridged carapace; small plastron

CO Genera:

1. Chelydra

Emydidae - Box & Pond Turtles

• Smooth shells

• large carapace & plastron compared to body

• webbed feet

• uniquely patterned plastrons

• able to retract head & limbs straight into shell (Cryptodira)

CO Genera:

1. Chrysemys

2. Terrapene

Genus: Chrysemys

CO species (1): C. picta

• smooth, brightly colored shell

• shell is relatively flat

• striped pattern on head

• colorful plastron

Genus: Terrapene (box turtle)

CO species (1): T. ornata

• high rounded upper shell

• hinged plastron

• patterned scutes

• more terrestrial, lacks webbing on feet

Kinosternidae - Mud & Musk turtles

• generally small turtles

• highly domed, oval-shaped carapace

• most have a plain shell w/ no pattern

• big head, pointed snoutx

CO Genus: Kinosternon

Trionychidae - Soft chell tutles

• Flattened bodies

• smooth, letheratherly, soft shells

• snorkel noses

• extensive feet webbing

CO Genus: Apalone

Dermochelyidae - Leatherback turtles

• largest of all turtle families

• leathery carapace embedded w/ osteoderms

• cannot fully retract head

• limbs modified into flippers

• weal jaw - only prey on jellyfish

only one extant species in this family

Cheloniidae - Sea turtles

• only turtles whose front limbs are stronger than back limbs

• large turtles

• oval or heat shaped carapace

• limbs modified into flippers

Testudinidae - Tortoises

• Largest of the land turtles

• Domed carapace

• Most have no hinge on plastron

• Thick legs

• Webless feet with short toes

• Very small brains

Pleurodira (suborder) - Side-Necked turtles

• retract necks sideways into shell (Pleurodira)

• large overhang of carapace

• 12 scutes on plastron

Crocodilian phylogeny

Crocodile Distribution and Hotspot

Distribution: Global

Hotspot: South America

Snout shape & Teeth

Alligator: broader snout, U shape & upper jaw teeth exposed

Crocodile: V shape snout, both mandibular and upper jaw teeth exposed

Gavialidae: slender long snout & needle-like teeth

Size

Feet

Color

Crocodilian overall traits

Scutes

• non-overlapping

• keratinous scales formed from dermis

• shed individually

• osteoderms underneath scutes

laterally compressed (keeled) tail

families can be distinguished by snout shape & teeth

Alligatoridae

4 genera, 8 species

Range: Central & South America also Eastern China

All mandibular teeth fit in upper jaw when mouth is closed

Broader snout (compared to crocodiles)

Caimans

• in the subfamily called Caimaninae

• Range: Mexico, Central & South America

• Relatively small crocodilians

  • adult size typically ~1.5-2 metes

Crocodylidae

2 genera, 13 species

Broadly distributed

Mandibular teeth exposed outside of upper jaw when mouth is closed

Narrower snout (compared to alligators)

Have salt glands that allow them to live in salty habitats

Range in size from 2-7 meters

Crocodylus porosus (saltwater croc) & Crocodylus niloticus (Nile croc) are the largest

Gavialidae

2 monotypic genera

Range: Margins of India & SE Asia

Long, slender snouts

Needle-like teeth

• Used to snag fish w/ a side a swipe of the mouth

Order: Rhynchocephalia - Tuataras

Only 2 species that are endemic to New Zealand, live on surrounding offshore islands

• Sphenodon punctatus

• Sphenodon guntheri

“Tuatara” is a Maori word meaning “peaks on back”

Rhychocephalia Distribution & Hotspot

Tuataras are a separate order from squamates, all other relatives are extinct.

Tuatara Traits

• Heavily fringed back

  • Fringes made from soft, triangular folds of skin

• Pronounced photoreceptive third eye

• No visible ear

• Distinct Jaw - 2 rows of teeth on upper jaw

• Rudimentary paired out-pocketing sex organ

• Diapsid, like lizards

• Nocturnal as adults

Hemipenes

Squamates (snakes & lizards) have hemipenes

There are 2 (hemi-) for doubling the chance of reproduction

Rhynchocephalia & Squamata Evolution

Skull identification

• two rows of teeth on upper jaw

• maxilla attached to premaxilla

• dentary ends in a bifurcate structure

• quadrate is thick and positioned further back

• supratemporal articulates with the quadrate but has limited motion

What bones make up squamate skull?

Maxilla, Dentary, Quadrate, Supratemporal

Squamate evolution: Snakes

• maxilla: has the ability to expand in order to allow them to eat in a more fluid and flexible manner

• dentary: their dentary is smaller in size and unfused, making it so that it can widen and allow them to eat prey this much larger than them

• quadrate: the dramatic angle of it ensures that he back jaw can widen quite a bit to allow for the successful consumption of large prey

• supratemporal: it is more forward so that other skull bones can move with impacting the brain

Squamate evolution: Lizards

• maxilla: meant to keep everything steady which accounts for its heftiness and sturdiness

• dentary: its structure coincides with the maxilla, allowing them to chew food in a more uniform manner

• quadrate: the angle of this structure makes it so that he mouth can only move in a particular direction and accounts for why they are not able to ‘unhinge‘ their jaw to take in prey that is much larger than them

• supratemporal: it is placed further back which leads to minimal movement while they are eating

Ambystoma mavortium - Western Tiger Salamander

• Blunt head, rounded mouth

• Large, thick body

• Costal grooves - very prominent

• Paddle tail

• Digit loss - 4 toes in front, 5 in back

• Can be paedomorphic

• Mottle yellow & blue/brown pattern

Lithobates pipiens - Northern Leopard Frog

• Pointed snout

• Distinct dorsolateral folds

• Light green halos around brown spots

• Tympanum present

• Muscular hindlimb

• Webbing on hind feet

Pseudarcris maculata - Boreal Chorus Frog

• Small bodied

• Triangular snout, small tympanum

• Mask on face that goes from tip of nose to groin

• 3 broken streaks/stipes down back

• Long digits & limbs

• Limited webbing

• COlor ranges from brown to green

Spea bombifrons - Plains Spadefoot

• Smooth skin

• Extensive toe webbing on back

• Presence of boss

• Spade on hind foot

• Small tympanum

Anaxyrus woodhousii - Woodhouse’s Toad

• Rough bumpy skin

• Parotoid glands

• Extensive webbing

• Tympanum present

• White dorsal stripe

Aspidoscelis sexlineata - Six-lined Racerunner

• plate-like scales on head

• granular scales on body

• visible ears

• narrow head

• six lines on back

Plastiodon multiviragtus

• rectangular head

• often have orange color around mouth

• ear hole present

• thick neck small bodied

• cycloid (fish-like) scales

• reduced/small limbs

• long tail relative to body

Holbrookia maculata - Common Lesser Earless Lizard

• granular scales

• rounded head, duck-like mouth

• no ear

• distinct eyelids

• busy pattern on back

• paired ventrolateral blotches on each side of belly

Scaloporus undulatus - Eastern Fence Lizard

• distinct eyelids

• keeled mucronate scales

• pattern on back can vary, often looks like chevrons

• blue bow tie often present on ventral side of neck

• blue patches on belly

Phrynosoma hernandesi - Greater Short - horned Lizard

• Round, flat body

• short limbs, short tails

• horned scales behind eyes & on back of head

• lateral fringe scales

• can eject blood from eyes when threatened

• pattern & coloration can vary, often with dark patches down back

Nerodia Sipendon - Common Water Snake

• large head, barred labial scales

• messy saddle pattern, slightly off/saddles don’t always connect, generally dark & black

• Keeled scales, large-bodied, divided anal scale

Pituophis catenifer - Gopher snake/Bullsnake

• large head, barred labial scales, distinct rostral scale

• large head plate scales, often with “unibrow” between eyes

• Large body, messy saddle pattern, like desert camo

• keeled scales, single anal scale

Crotalus viridis - Prairie Rattlesnake

• wide head, many small scales on head, white stripes frame mask on face

• saddle pattern, short wide body, large rattle

• elliptical/slite pupils, single anal scale

Tantilla nigriceps - Plains blackhead snake (Tantilla gracilis specimen)

• flat head, round rostrum, large head plate scales

• small body, black head, light body, smooth scales, divided anal scale

Lampropeltis trianngulum - Milksnake

• Rounded head, banded pattern, large plate scale on head

• distinct aposematic color pattern, smooth + glossy scales, single anal scale

Coluber constrictor - North American Racer

• angular head, distinct supraocular scale, long tail & body

• light colored mandible/jaw, can be black/blue to green

• cream or yellow belly with no pattern

• smooth scales, divided anal scales

Thamnophis radix - Plains Gartersnake

• checkered pattern bw stripes on body

• bright dorsal stripe, rectangular head, distinct supraocular scale

• blunt rostrum, large eyes, round pupils, barred labial scales

• keeled scales, single anal scale

Heterodon nasicus - Plains Hog-nosed snake

• blunt & wide head, mask on face with unibrow, barred labial scales

• upturned rostral scale, saddle pattern, dark belly scales

• keeled scales, divided anal scale

Terrapene ornata - Ornate Box turle

• domed carapace

• pattern scutes

• hinged plastron

• females have yellow eyes, males have red eyes

• spotted legs, no webbing on toes

Chrysemys picta

• smooth flat carapace

• full plastron

• extensive foot webbing

• yellow streaks on face

• red color on outer scutes

• small tail