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Family Parasuchidae

(= Phytosauridae)

Rutiodon
Rutiodon
illustration by Steve Kirk - Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals, ed.. Barry Cox

The Phytosaurs (this unfortunate name means "plant lizards", because it was originally mistakenly believed that petrified.mud fillings in the jaw of the first specimen found were herbivore teeth) were crocodile-like semi-aquatic thecodonts that suddenly appeared and became very abundant during the latter part of the link to palaeos com Triassic period.

They are more appropriately known by the later (but less widely used) name Parasuchia ("alongside the crocodiles"), as they resembled link to palaeos com crocodiles to a remarkable degree in size, appearance, and life-style.  This is an amazing illustration of convergent or parallel evolution.  Phytosaurs were in a sense "crocodile uncles", since both Phytosaurs and proto-crocodiles shared a common ancestor in early Pseudosuchian thecodonts.  But true crocodiles were only able to evolve after phytosaurs became extinct at the end of the Triassic.

The differences between phytosaurs and crocodiles are minor.  The most obvious differences between phytosaurs and crocodiles are in the position of the nostrils.  Phytosaurs had nostrils placed near or above the level of the eyes.  Crocodiles have nostrils placed far forward at the tip of the snout.  Another difference is in the palate (roof of the mouth).  True crocodiles have a secondary palate that enables them to breathe when partially submerged, even though the mouth is full of water.  Phytosaurs lacked this adaptation, and used the nostrils on top of the head in order to swallow air while underwater.  Phytosaur limbs were also somewhat more primitive in structure than those of crocodiles. Fossil footprints indicate however that phytosaurs could move in a semi-erect stance on land and did not drag their tails as modern crocodiles do.

Phytosaurs were if anything even better armoured than crocs, with the throat and back of the animal being are protected by heavy armoured scutes, and the belly reinforced with a dense ararngement of abdominal ribs (see illustration below).

Phytosaurs are divided into two subfamilies (recently sometimes considered distinct families): the Mystriosuchinae and the Angistorhininae (= Rutiodontidae).

Parasuchus
skeleton of Parasuchus, showing the abdominal ribs and the long slender Mystriosuchine skull
length overall 2.5 meters
link to palaeos com Carnian age - widespread
source: external link Great Triassic Assemblages Pt 1 - The Chinle and Newark - Professor Paul Eric Olsen.

The Mystriosuchinae represent the more primitive group.  They tend to have gavial-like skulls (e.g. Mystriosuchus, Parasuchus) with a long, slender snout tipped with a pronounced tusked "hook," and jaws lined with uniform conical teeth.  These were clearly fish eaters.

The Angistorhininae were more heavily built with crocodile- or alligator-like skulls (e.g Nicrosaurus, Rutiodon) characterised by a shorter, wider, deeper snout, and jaws equipped with serrated blade-like fangs and more cylindrical crushing-type teeth.  These clearly fed on large animals, specifically other tetrapods.

However the situition is not so clear cut, as some Mystriosuchines had Angistorhininae characteristics and some Angistorhinines had Mystriosuchine characters - indicating the two morphotypes evolved independently in both lineages


Parasuchidae (=Phytosauridae)

lifestyle: large to very large semi-aquatic carnivores, equivalent to modern-day crocodile 
environment: freshwater rivers, lakes, and swamps
food: fish and smaller tetrapods 
enemies: no animal would be stupid enough to take on a large adult phytosaur
size: from 2 to 8 or even 12 meters (average 3 to 6 meters)
probable ancestor: unspecified early Pseudosuchian
known time range:Late link to palaeos com Carnian to link to palaeos com Rhaetian
known distribution: Europe, India, North Africa and North America
status: monophyletic




links - Phytosaur - Links -
links

Phytosauria Translation and Pronunciation Guide - Ben Creisler - includes every known genus of phytosaur (Parasuchia)

web pagephotosGreat Triassic Assemblages Pt 1 - The Chinle and Newark - Professor Paul Eric Olsen.- includes information on Phytosaurs

web pagephotosThe Mesozoic Era includes phytosaur photos by Pamela Gore (Georgia Geoscience On-Line )

more links to be added....

References


Sankar Chaterjee "Late Triassic Dockum vertebrates: their stratigraphc and paleobiolographic significance"; in The Beginning of the Age of Dinosaurs. Kevin Padian, ed., Cambridge University Press, 1986
Long, R. A. & P. A. Murry, 1995. Late Triassic (Carnian and Norian) Tetrapods from the Southwestern United States. New Mexico Museum of Natural History & Science. Bull. 4. 254pp.





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page by M.Alan Kazlev
page uploaded 18 October 1999. Reposted and last modified 30 August 2005, links updated 16 January 2010

page uploaded 20 December 1998
modified 23 October 1999