Crocodylia (CROCS) Flashcards
What are some diagnostic features of crocodylians? (9)
Diapsid with two clear temporal fenestrae, mandibular fenestra on lower jaw, elongated jaw with socketed teeth (thecodont), body covered with protective osteoderms, vertebral ribs of trunk bar have cartilaginous uncinate process, has gastralia on abdomen, heart with four chamber, true penis, ankle with crurotarsal joint
How do crocs locomote in water? What are the two ways?
They propel themselves in water by undulating their tail and steering mostly with their hindlimbs.
Swimming: paddle with their webbed hind legs for slow swimming and fold their legs close to their body for streamlining and use tail for undulations in fast swimming
Lurking and hunting: swim very slowly with just eyes and nostrils above the water
How do crocs locomote on land?
They “belly crawl” in a sprawling posture for short distances or for fast/slow motions
They “high walk” with their forelimb and especially hindlimb erected for sustained locomotion
How does a croc “gallop”?
They push off with both hindlimbs and land on both forelimbs
Describe croc predation
They are all semi-aquatic ambush predators and they have pressure receptors on their head and body to sense the movement of prey, and they may jump out of the water to scare the prey. Typically they drag the tetrapod prey underwater so they drown
What are the three ways that crocs process their food?
- Swallow it whole
- Rip apart large prey by wedging it between underwater branches and roots
- Death rolling around their cranio-caudal axis
TRUE OR FALSE: Crocs have a strong closing jaw mechanism but a weak opening jaw mechanism (muscles)
TRUE
How to crocs thermoregulate?
They are all ectothermic therefore they rely on the environment to maintain optimal body temp of 30-33, to increase their body temp they bask in the sun and to cool down they open their mouths or hide in shaded bushes and water
Describe croc reproduction
Internal fertilization with the true penis (retracts into the cloaca when not in use), oviparous and lay hard shelled eggs, sex determination is temperature dependent
Female crocs guard the nest/hatchlings, and the unabsorbed egg yolk is encapsulated into the abdomen when hatching to provide nutrients
What are the three clades of Crocodylian?
Gavialidae, Crocodylidae, Alligatoridae
What are some diagnostic features of Gavialidae? (9) What is the only species in this clade?
Gavialis gangeticus, most aquatic clade of crocs, piscivorous, large adults, needle-like homodont teeth, long/slender snout, mature males have swollen tissue near the external naris, nasal passageway with enlarges bulla and a sulcus present near the orbit, quadrate is reflected ventrally
What are the diagnostic features of Crocodylidae? What is the species that is often confused with the gharial?
Often narrow snout, 4th tooth on lower jaw fits into notch on the upper jaw and can be seen, sharp/pointy teeth (not as slender as gharial), LINGUAL salt gland in the mouth
Tomistoma schlegelii: false gharial, elongate snout and needle like teeth
What are the diagnostic features of Alligatoridae? What is the species known as the “mud/pig dragon”?
2 alligators, 6 species in 3 genera of caiman, broad U-shaped snout, 4th lower jaw tooth fits into indent in upper jaw and is visible, front teeth are sharp/pointy but back teeth are round, NO lingual salt gland, complete nasal bar
Alligator sinensis: mud/pig dragon, small, vocalize before rainfall, live/hibernate in burrows
What are archosaurs?
Refers to the diversity and abundance of dinos which include predominant large terrestrial vertebrates in Jurassic and Cretaceous
Describe primitive archosaur skull fenestration.
Diapsid skull, antorbital fenestra, mandibular fenestra in lower jaw,
