Procompsognathus

''Procompsognathus'' is an extinct genus of coelophysid theropod dinosaur that lived approximately 210 million years ago during the later part of the Triassic Period, in what is now Germany. ''Procompsognathus'' was a small-sized, lightly built, ground-dwelling, bipedal carnivore, that could grow up to 1 m (3.3 ft) long.

Discovery and naming

The fragmentary and poorly preserved skeleton of ''Procompsognathus'' was found in the Middle Stubensandstein member of the Löwenstein Formation at the ''Weiße Steinbruch'', the quarry of Albert Burrer on the northern slopes of the Stromberg region near Pfaffenheim in Württemberg, Germany. The discovery was made by Albert Burrer in the spring of 1909 in white sandstone and gray/blue marl sediments that were deposited during the Norian stage of the Triassic period, approximately 210 million years ago.

The holotype SMNS 12591, consisted of three blocks of sandstone: one showed a small, seven-centimetre-long, severely crushed skull with lower jaws. The second and third contained the partly articulated remains of a postcranial skeleton, including twenty-nine vertebrae of the neck, back and tail; ribs; elements of the shoulder girdle and a forelimb; an ilium; both pubis and the hindlimbs. It represents an adult individual.

Burrer sent the specimen to Professor Eberhard Fraas of the ''königliche Stuttgarter Naturalienkabinett''. In a lecture on 9 October 1911, Fraas referred to it by the name " Hallopus celerrimus", considering it a jumping form of dinosaur that was approximately long, and was associated with the origin of birds. Later, Fraas decided to use a different name in the official publication. Fraas in 1913 named the genus ''Procompsognathus'' with as type species, ''Procompsognathus triassicus''. The type specimen is housed in the collection of the State Museum of Natural History in Stuttgart, Germany.

In 1921, Friedrich von Huene referred two more specimens, both also found in the Burrer quarry, in 1908, to ''Procompsognathus'': SMNS 12352, a partial skull and lower jaws from a larger individual than the holotype, and SMNS 12352a, an isolated left hand.

The genus name ''Procompsognathus'', means "before elegant jaw", and is derived from the name of another dinosaur, ''Compsognathus''. A later (Jurassic) small predatory dinosaur, ''Compsognathus'' takes its name from the Greek word ''kompsos'' (κομψός) which can be rendered as "elegant", "refined" or "dainty" and the Greek word ''gnathos'' (γνάθος) which means "jaw". The prefix ''Pro'' (προ) implies "before" or "ancestor of", although this direct lineage was not supported by subsequent research. The specific name ''triassicus'' refers to the geologic time period to which this dinosaur belongs, the Triassic.

Description

''Procompsognathus'' may have been about long,Holtz, Thomas R. Jr. (2011) ''Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages,'
Winter 2010 Appendix.
/ref> though Fraas in 1913 estimated a length of . In 2010 Gregory S. Paul gave an estimate of for the weight with a length of . In 2016, the holotype gained estimates of 1.3 kg and 28 cm in height at the hips. A biped, ''Procompsognathus'' had long hind legs, short arms, large clawed hands, a long slender snout with many small teeth, and a stiff tail. The femur discovered for the type specimen of this genus measures 93mm and the tibia, 112mm. The tibia is approximately 20% longer than the femur in ''Procompsognathus'', an adaptation which has been strongly correlated with the development of cursorial habits in dinosaurs, suggesting that they were good runners.

Distinguishing anatomical features

A diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms. Some, but not all, of the features in a diagnosis are also autapomorphies. An autapomorphy is a distinctive anatomical feature that is unique to a given organism or group. In 2000, Rauhut noted that its scapula is more slender than that of '' Coelophysis bauri''.

In 1998 Chatterjee noted that the skull of ''Procompsognathus'' possesses a suite of theropod synapomorphies, which included:
* the presence of an accessory maxillary fenestra
* the vomers are fused rostrally and are extended considerably forward to the choana
* the single quadrate head is received completely by squamosal without paroccipital contact
* the lateroshenoid possesses a transverse postorbital process
* the orbitosphenoids are fused

Classification

Type specimen SMNS 12591

While it is undoubtedly a small, bipedal carnivore, the extremely poor preservation of the only known ''Procompsognathus'' fossil makes its exact identity difficult to determine. Fraas originally assigned it to the Dinosauria. In 1923 Franz Nopcsa coined a Procompsognathinae, and in 1929 von Huene created a Procompsognathidae, though these concepts are today rarely used. In 1932 von Huene saw it as a member of the non-dinosaurian Pseudosuchia. It has since then usually been considered a theropod dinosaur, with some exceptions. In 1992 Paul Sereno and Rupert Wild stated that the holotype specimen consisted of fossils from two separate animals: the postcranial skeleton would be a theropod, likely a coelophysoid related to '' Segisaurus'', but the skull and the von Huene specimens they referred to the basal crocodylomorph ''Saltoposuchus connectens''. However, in 1993 Sankar Chatterjee after further preparation refuted their assessment and regarded the skull as that of a theropod similar to ''Megapnosaurus'', and demonstrated that it could not have been a crocodylomorph, as it lacks the landmark features of this group.Chatterjee, S., 1998, "Reassessment of the ''Procompsognathus'' skull", p. 6 in: Wolberg, D.L., Gittis, K., Miller, S., Carey, L., and A. Raynor (eds.), ''Dinofest International''. The Academy of Natural Sciences, Philadelphia Sereno (1997) and Ezcurra and Novas (2007) conducted phylogenetic analysis that supported the placement of ''Procompsognathus'' in the taxon Coelophysidae. This genus may be most closely related to '' Segisaurus halli''.

Referred specimens SMNS 12352 and SMNS 12352a

Much controversy has arisen however, about the association with the later material referred by von Huene. In 1982 John Ostrom claimed that SMNS 12352 and SMNS 12352a originated from a taxon different from the holotype. In 2006 and 2008 Fabien Knoll concluded that SMNS 12352 represented a crocodylomorph and SMNS 12352a a crocodylomorph or some other basal archosaur. The postcranial skeleton, for which he reserved the inventory number SMNS 12591, was a coelophysoid; and the skull, now indicated with the number SMNS 12591a, a perhaps more derived theropod, possibly a basal member of the Tetanurae. In 2012 Knoll after a CAT-scan reaffirmed that SMNS 12352 was a crocodylomorph, but established it was different from ''Saltoposuchus''.

Oliver Rauhut and Axel Hungerbuhler (2000) noted features of the vertebrae which suggest that ''Procompsognathus'' may be a coelophysid or ceratosaur, and Carrano ''et al.'' (2005), in their re-study of the related genus '' Segisaurus'', found both ''Segisaurus'' and ''Procompsognathus'' to belong to the Coelophysidae within Dinosauria. In 2004 David Allen considered ''Procompsognathus'' to be a primitive, non-dinosaurian ornithodiran.

Paleoecology

''Procompsognathus'' lived in a relatively dry, inland environment and may have eaten insects, lizards and other small prey. Contemporaries of ''Procompsognathus'' included the coelophysoids '' Halticosaurus'' and '' Dolichosuchus'', as well as the Sauropodomorphs ''Plateosaurus gracilis'' and '' Efraasia minor''. Weishampel, ''et al.'' (2004) noted that theropod tracks and fossils of an unnamed herrerasaur genus are known from the Lower Stubensandstein.Baden-Wurrtemberg, Germany; 1. Lower Stubensandstein," in Weishampel, ''et al.'' (2004). Page 524.

In popular culture

''Procompsognathus'' appears in the novel ''Jurassic Park'' and its sequel '' The Lost World'' by Michael Crichton. The species is sometimes referred to as "compys" by the characters. While the author invents a venomous bite for ''Procompsognathus'' with soporific effects, there is no evidence to support venom in ''Procompsognathus''.

References

{{Taxonbar, from=Q131446

Coelophysoids
Norian life
Late Triassic dinosaurs of Europe
Triassic Germany
Fossils of Germany
Fossil taxa described in 1913
Taxa named by Eberhard Fraas