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The Terrestrisuchus can best be described as a lizard-like land crocodile. It is a tetrapod and a crocodylomorph. They grew to be approximately 0.75 to 1 meter long and had an average weight of 15 kilograms. They were found in the Late Triassic period (Revolvy). The first Terrestrisuchus was found by P. J. Crush in 1984 in Wales (FossilWorks). It had legs that were fairly long and that did not support the body from the sides but underneath. It is a digitigrade, which means that it walks on its toes.
It has been debated and questioned that the Terrestrisuchus is just the adolescent form of the Saltoposuchus (Prehistoric Wildlife, 2011).
Comparing the legs of the Terrestrisuchus to other similar-looking modern-day bone structures, it appears that the legs must have been used to run and gallop. The Terrestrisuchus was a brisk and limber predator of small organisms (Prehistoric WIldlife, 2011).
Because the limbs were positioned directly beneath the body, we can conclude that the legs worked as pairs for galloping.
Modern crocodiles are known to use paired walking, pseudo-galloping (Revolvy).
Figure 2: The bone structure of the Terrestrisuchus compared to other bone structures of modern creatures such as a greyhound. Notice how the leg structure is similar (Lyell Collection Geological Society Publications, 2013)(ArtGraphica, 2017).
The Saltoposuchus is very similar to the Terrestrisuchus. It is like a small theropod (beast-footed) dinosaur. The long hind legs would have allowed it to cover more distance with each stride. It had small teeth that were adapted for capturing small vertebrates as prey (Prehistoric WIldlife, 2011).
Each of these crocodylomorphs has been considered bipedal. “The Terrestrisuchus had a smaller skull and longer neck but was otherwise virtually identical to Scleromochlus. (The Pterosaur Heresies, 2011)
The quadratojugal is parallel-sided and the squamosal lacks a descending process. A hard secondary palate is formed by the maxillae and premaxillae. A fenestra pseudorotundum is present but the pterygoids were not sutured to the braincase. The Eustachian tubes were ramified. A prearticular is present. The teeth are recurved, flattened, and bear serrations. The ischium projects posteriorly and the pubis, bearing an obturator foramen, borders the open acetabulum. The posteroventrally extended coracoid joins the ossified dorsal vertebrae are primitive. A paired row of leaf-shaped dorsal skutes was present. The earliest crocodiles are placed in three suborders—Protosuchia, phenosuchia, and Triassolestia. (Crush, P.J. 1984)
In 1984, Crush created a complete skeleton of the Terrestrisuchus. The elements came from a fissure fill and needed to be reassembled as if they were puzzle pieces. Crush (Fig.4) put the hand together with a small thumb, similar to a human hand.”(The Pterosaur Heresies, 2011)
Small terrestrial crocodilian; skull bones unornamented; skull table rounded; supratemporal and antorbital fenestrae elongated; frontals and parietals paired; postorbital bar superficial; otic notch formed; quadrates bear conche, slope anteriorly, and buttress under the squamosals; quadratojugal parallel sided; nineteen maxillary teeth; maxillae and premaxillae form a secondary palate; anterior palatal fenestrae present; interpterygoid vacuities present; basipterygoid articulations movable; pterygoids not sutured to the braincase; pterygoid flanges formed; Eustachian tubes ramified; fenestra pseudorotunda formed; external but no internal mandibular fenestra present; prearticular present; no pronounced retroarticular process; articular fenestrated and possessing a dorsally directed, medial, process; teeth thecodont, recurved, flattened, bearing anterior and posterior cristae and serrations; vertebrae platycoelous; neural spines low; about twenty-four presacrals; two sacrals; about seventy caudals; all presacrals bear free ribs; costal articulations fuse only on the last presacral; dorsal ribs bear only anterior flanges; double row of dorsal, ornamented, leaf-shaped skutes; pectoral girdle lacks clavicles; ossified sternum present; slender interclavicle present; coracoids extended postero-ventrally; supracoracoid foramen present; scapula expanded into pints anteriorly and posteriorly; limb bones hollow; humerus with a well-developed deltopectorial crest; ulna bears a slight olecranon; carpus crocodilian; only one distal carpal; ilium with pre- and post-acetabular processes; supra-acetabular crest well developed; acetabulum perforated; pubis entered acetabulum; obturator foramen present; ischium projected posteriorly; pelvic symphysis present; femur with a fourth but no lesser trochanter; tarsus crocodilian; metatarsal five reduced but bearing two phalanges; metatarsals one to four subequal in length. (Crush, P.J.1984)
Terrestrisuchus is considered to be a crocodile because of the presence of elongated radiale and ulnare, whose structure can be homologized with those bones of the modern crocodile. Other apomorphic characters for the order Crocodylia, present in this genus, are the absence of a descending process from squamosal to quadratojugal and the presence of a parallel-sided quadratojugal. (The quadratojugal of Pseudohesperosuchus is assumed to be specialized.) Terrestrisuchus has other character states considered by Langston (1973) and Nash (1975) to be diagnostic of the Crocodylia: external nares terminal in position; some development of a secondary palate; choanae posterior to the external nares; quadrate inclined and bordered by a long slender fourth quadratojugal; pterygoids wide with deep wings; advanced crurotarsal joint; femur without a marked fourth trochanter and no development of a greater trochanter; external surfaces of the dorsal scutes sculptured.(Crush,P.J.1984)
Observing the bone structure of Terrestrisuchus, one can conclude that it was bipedal, or walked on two legs. The tail must have been used to keep balance when running from other predators or chasing prey. The teeth were carnivorous as they look to be used to tear and not grind. I agree with the previous reconstructions and do not think that there should be a change. However, it is proposed that the Terrestrisuchus is a juvenile form of the Saltopus. I disagree because the bone structures have many noticeable differences and the bone structure of an adolescent stays the same when it matures into an adult.
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