Gerrothorax pulcherrimus (Hellrung ). Plagiosaurids were a small clade of apparently water bottom-dwelling, flattened temnospondyls with broad skulls. On the left their arrangement is similar to that in the Kupferzell Gerrothorax ( Hellrung, fig. 17). The three curved ceratobranchials, which are aligned. Gerrothorax pustuloglomeratus, after Hellrung (): B, dorsal; E, has been referred to Plagiosuchus pustuliferus by Hellrung (), but.
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Temnospondyli from the Middle Triassic of Germany: The cranial anatomy of the plagiosaurid temnospondyl Plagiosuchus pustuliferusfrom the Middle Triassic of Germany, is described in detail on the basis of a newly discovered skull and mandibular material.
The highly derived skull is characterized by huge orbitotemporal fenestrae, a reduction of the circumorbital bones—the prefrontal, postfrontal and probably postorbital are lost—and the expansion of the jugal to occupy most of the lateral skull margin. Ventrally the extremely long subtemporal vacuities correlate with the elongate adductor fossa of the mandible.
The dentition is feebly developed on both skull and mandible. The remarkably divergent cranial morphology of P. Specific structural aspects of the skull—including an extremely short marginal tooth row, feeble dentition and an elongated chamber for adductor musculature—together with evidence for a hyobranchial skeleton, suggests that P. Plagiosauridae, an enigmatic group of Triassic temnospondyls, are characterized by a highly modified skeletal morphology that appears to have been entirely adaptated for an exclusively aquatic, bottom-dwelling existence Nilsson, ; DeFauw, ; Hellrung, Within this general bauplan, the adequately known members of the group display remarkably divergent, highly autapomorphic cranial morphologies.
The most recent review of the Plagiosauridae, which includes a summary of the taxonomic history of the group and details on the locality, horizon and synonyms for each species, was published by Hellrung In the most recent review of plagiosaurid systematics Hellrung,these were delimited as follows.
However, our knowledge of the anatomy of these genera is decidedly patchy. In stark contrast, the remaining genera are largely represented by scant cranial and postcranial remains. With regard to the plagiosaurids known from Germany, Plagiosternum is known from one near-complete, albeit poorly preserved, skull Warren,one partial skull roof von Huene,and other fragmentary cranial and postcranial remains Fraas,; von Huene, ; Plagiosaurid is known from a partial skull and postcranial remains Jaekel, ; and Plagiosuchus is known from a poorly preserved skull and postcranial remains Fraas, ; von Huene, Likewise, the Russian Plagiosternum spp.
The plagiosaurid material belongs to the genera GerrothoraxPlagiosternum and Plagiosuchus. A review of the Gerrothorax material has recently been published Hellrung,while the Plagiosternum material has recently been described Gastou, This paper will extend the current investigations of the Plagiosauridae by describing the first complete skull of Plagiosuchus. This specimen featured pustular type ornamentation, and on that basis von Huene referred the specimen to P.
Moreover, von Huene demonstrated that in the gross morphology of the skull and pectoral girdle, P. Accordingly, he transferred P. Further fragments attributed to Plagiosuchus pustuliferus have been reported Hellrung,but our knowledge of the anatomy of this taxon has rested almost exclusively on von Huene’s description. Here we provide a detailed description of the cranial anatomy of Plagiosuchus pustuliferusidentify a number of autapomorphies of the species, and present a restoration of the skull and mandible.
Plagiosauridae – Wikipedia
We also compare the skull of P. Finally, we consider aspects of the palaeobiology of P. Specimens of Plagiosuchus pustuliferus examined in this study, together with locality and horizon information, are listed below. Specimens figured in this paper were photographed digitally, and the resulting images manipulated in Adobe Photoshop. The interpretive drawings were produced by R.
Partial skull, partial left and right mandibles, and anterior part of the postcranium including the pectoral girdle. Lettenkeuper, Ladinian upper Middle Triassic. Described and figured by von Huene Near-complete skull and left mandible, six trunk vertebrae including the atlas and axis, and additional fragmentary postcranial remains. Skull and mandible figured in Hellrung Dentary portion of a right mandible, in two fragments.
Locality and horizon as for SMNS Disarticulated partial skeleton, including cranial fragments. Left cheek fragment, including part of the tabular, squamosal and quadratojugal. Oberer Lettenkeuper, Ladinian upper Middle Triassic. Left postparietal, a centrum and a neural arch. Near-complete but disarticulated postcranial skeleton, a near-complete right mandible and fragments of the skull.
A comprehensive list of synonyms and citations to Plagiosuchus pustuliferus in the literature is provided by Hellrung Hence, the synonymy list above is restricted to changes in the taxon name.
Designated lectotype by Hellrung Cranial diversity within the Plagiosauridae. Hwllrung, dorsal; D, ventral views. Gerrothorax pustuloglomeratusafter Hellrung B, dorsal; E, ventral views. Plagiosternum granulosumafter Gastou C, dorsal; F, ventral views. SMNSa partial skull and anterior postcranium described and figured by von Huene Additional fragmentary material has been referred to Plagiosuchus pustuliferus by Hellrungbut none of this was figured or described.
Stratigraphically, the species ranges from the Grenzbonebed Oberer Muschelkalk, Ladinian to the overlying Lettenkeuper, where it has been recorded in three horizons Vitriolschiefer, Sandige Pflanzenschiefer, Untere Graue Mergel Hellrung, The cranium of Plagiosuchus pustuliferus can be distinguished from all other plagiosaurids by a suite of autapomorphies, as follows: Except where specified, the following description of the skull of Plagiosuchus pustuliferus is based on SMNS Fig.
The state of preservation of the specimen is poor, with clear evidence of strong dorsoventral compaction: The suspensorial region on the right side of the skull has also been pushed forward significantly.
Not surprisingly, many of the dermal roofing elements, especially in the posterior part of the skull, have been displaced to varying degrees.
Some areas of missing bone have have been filled with resin. A large hole in the midline of the skull anteriorly may or may not represent a natural vacuity, as discussed in the text. When found, the associated left mandible was pressed against the palate such that its ornamented labial surface terrothorax left sculptural impressions on the proximal part of the cultriform process of the parasphenoid, the ventral surface of the right gerrothkrax and the basipterygoid ramus of the right pterygoid.
Plagiosuchus pustuliferusSMNS Photographs of the skull in: A, dorsal; B, ventral; C, occipital views. Despite the preservational state, and with the exception of the premaxillae, all dermal elements of the skull are evidently preserved. For the most part, individual bones are readily defined because they have separated from neighbouring elements, especially in the posterior region of the skull.
Although distorted to some degree, some basic measurements of SMNS are provided as a guide to its general proportions. The preserved length of the skull roof is approximately mm measured from the front of the nasals to the posterior margin of the postparietals, and mm to a line across the posterior margin of the occipital condyles.
These measurements probably represent the maximum possible length of the skull in life, taking into account the absence of the premaxillae, skull compaction and displacement of various elements. At its widest point across the quadratojugals the skull measures mm; this is probably a little greater than in life because of compaction especially in the right suspensorial region.
Hence, in overall outline the skull is distinctly parabolic and is only moderately wider than it was long. In common with other plagiosaurids, the occipital condyles projected well beyond the posterior margin of the skull roof. The reconstructed skull shape presented by von Huene In terms of sutural morphology, it would appear that the dermal roofing bones were, for the most part, rather loosely sutured to adjoining elements.
The thickness of the bone of the skull roof is difficult to assess because of the complex nature of the ornament described below. Nevertheless, it is clearly thickened where ornament is most intensely developed, reaching up to approximately 7 mm inclusive of ornament. This is evident especially in the anterior regions of the jugals, the lateral flanks of the parietals and on the squamosals where damage has exposed the bone in section.
Where ornament is poorly developed such as on the lateral flanks of the frontalsor where it peters out toward the peripheral margins of an element such as on the anterior margin of the postparietalsthe dermal bone is very thin, up to approximately 2 mm.
The ornamentation is in the form of bulbous, irregular tubercles of varying height up to c. These are often connected with neighbouring tubercles to form a more complex tubercle network. In some areas—such as on the presumed centre of ossification of the postparietals, the anterior part of the jugals and on the nasals—the tubercles are extensively interconnected so that shallow pits of varying diameter up to 5 mm and depth no more than 2 mm develop between them.
Here, the ornament resembles the reticulate variety typical of most temnospondyls, except that in Plagiosuchus pustuliferus the walls separating the pits are markedly thickened and always rounded dorsally. Where the pits are clearly visible, a single, tiny foramen pierces the pit floor. Elsewhere on the skull roof, the interconnected tubercles form prominent, elongate ridges, evident in particular on the jugals, parietals and postparietals.
A much elongated ridge spans the length of the frontal bone near the midline; the plane of each frontal slopes ventrally from this ridge toward the orbitotemporal rim, where the bone is rather thin. In some areas, the tops of the ridges are themselves finely pitted.
Interpretive drawing of the skull in dorsal view, with bones indicated on the lower figure.
File:Gerrothorax – Wikimedia Commons
Only parts of the sensory line system can be identified, probably because of the state of preservation of the specimen. It forms a continuous, well-defined sulcus that traverses the length of the bone possibly crossing onto the? The floor of the sulcus anterior to the flexure is formed by a series of shallow pits, whereas posteriorly the floor is more terrothorax less smooth.
The sulcus on the jugal in SMNS may be interpreted in one of two ways. First, it may hellryng the infraorbital sulcus only, in which case the jugular and temporal sulcus, if present, diverged from the infraorbital sulcus in a more posterior position i. Second, it may include the infraorbital sulcus anteriorly and the jugular sulcus posteriorly, with the temporal sulcus being undefined. Elsewhere on the skull roof, each tabular has a depressed strip of weakly sculptured gerrotyorax on its posteromedial margin which evidently continues onto the postparietals evident on the right but not the left postparietal which is partially covered by the tabular.
The most striking features of the skull roof Fig. In addition, their shape is clearly highly irregular: In the snout region of the skull there is a rectangular cavity which separates the nasals along gerrtohorax entire length. The medial margin of each nasal is very thin and gerrofhorax cannot be determined whether the margins are of finished bone.
A conservative appraisal of this area would be that the nasals have separated along their length post-mortem. However, the possibility that the opening represents a natural vacuity cannot be discounted.