Lab 6: Serpentes & Ophidia: Matt Knestrick & Megan Thornhill

Overview: In this lab, we examined the family of reptiles known as serpents. We examined skull specimen to show their unique skulls, and examine preserved and live specimen of a few major serpents families.

Skull

The skull photographed is that of the genus Crotalus. The skull exhibits both aglyphous and proeteroglyphous fangs. Aglyphous are typical fangs found in all serpents, while proteroglyphous are “front-fangs” found at the front of the mouth attached to to maxilla. This skull is an excellent example of the streptosytly seen in snakes. Streptostyly is a method of opening the mouth where the long jaw articulates on the quadrate bone. Because of the exaggerated jaw-quadrate bones on the snake (compared to humans or other mammals), snakes can open their mouths extremely wide to swallow prey that can be much bigger than their heads.

Familes

We studied 5 major families of snakes, as well as saw specimen native to Ohio.

Pythonidae

The pythons are Old world serpents, meaning that their distribution are in Africa, Asia, Indonesia, etc. They are aglyphous and are some of the largest snakes in the world.

Boidae

Boidea is the boa family. They are composed of two major subfamilies: Boinae and Erycinae, and have an old and new world distribution, occurring in Western N. America, The West Indies, S. Asia, and Madagascar. Like pythonidae, they are aglyphous.

Viperidae

The viper family has 4 major subfamilies: Azemiopi (1 genus), Viperinae (13 genera), and Crotalinae (26 genera). Subfamily Crotalinae are venomous, and mostly viviparous (live birth), although some are oviparous (lay eggs). Similarly, some have rattles, a derived condition, while others do not. They are long-lived, and have cranial infrared receptors associated with their loreal pits. Crotalinae have aglyphous fangs, as well as solenoglyphous ones. Solenoglyphous fangs are highly derived, hollow front fangs that are attached to a highly mobile maxilla bone.

There are also OH native species in the Crotalinae subfamily, such as:

Agkistrodon contortrix (Northern Copperhead)

Sistrurus catenatus (Eastern Massassauga)

Crotalus horridus (Timber Rattlesnake)

The second subfamily is Viperinae. Unlike Crotalinae, Viperinae have lost their loreal pits. They are ovi- and viviparous, and are terrestrial, nocturnal species. They also have a large old world distribution, including Africa, Asia, and Europe.

Elapidae

The Elapids are cobras, sea snakes, and death adders. There are over 60 genera, distributed from southern N. America to S. America, Africa, Asia, and the Indian and Pacific oceans. They are highly venomous, with no cranial infrared receptors. They have proteroglyphous fangs.

The subfamily Hydrophiinea includes sea snakes. These species have laterally compressed, paddle-like tails. They have lost their large, ventral scales, and are viviparous, although some are oviparous and lay eggs on land. The subfamily Elaphinae are the cobras, mambas, and sea cretes. They are Opheophagus, or snake eatere, and are mostly terrestrial and oviparous.

Colubridae

The Colubridae are one of the largest families of snakes. They are highly diverse “grab bags” or species. However, they are a monophyletic group, and are all typically non-venomous (at least to humans).

The first subfamily is Colubrinae. This is the most diverse subfamily, with over 100 genera. There are also many OH native species, including:

Opheodrys aestivus (Rough Green Snake)

Coluber constrictor foxii (Blue Racer)

Coluber constrictor constrictor (Northern Black Racer)

Pantherophis vulpinis (Fox Snake)

Lampropeltis triangulum (Eastern Milksnake)

Lampropeltis getula (Black Kingsnake)

The second subfamily, Natricinae, are semi-aquatic and entirely aquatic snakes. They are typically fish and amphibian food specialists. They also have many OH natives, including:

Nerodia sipedon (Northern Water Snake)

Regina septemvittata (Queen Snake)

Thamnophis sirtalis (Eastern Garter Snake)

Storeria dekayi (Brown Snake)

Storeria occipitomaculata (Northern Redbelly Snake)

The final subfamily is Dipsadinae. Dipsadinae have two different body types, depending on their activity during the day. Dirunal species typically have more robust, muscular bodies, while nocturnal species have more slender bodies. They are terrestrial and oviparous, and their clutch size is directly related to the size of the female. They are also Opisthoglyphous, meaning they have teeth in the rear of their mouths. They include the following OH native species:

Diadophis punctatus (Ringneck Snake)

Heterodon platyrhinos (Eastern Hognose Snake)

Carphophis amoenus (Worm Snake).