The sutural pattern of skull-roof bones in Lower Permian Discosauriscus austriacus from Moravia JOZEF KLEMBARA Klembara, J. 1994 06 15 The sutural pattern of skull-roofbones in Lower Permian DiKosauricN LETHAIA alcmiacuc &om Moravia. Lethaia, Vol. 27, pp. 85-95. Oslo. ISSN 0024-1 164. Sutures between ornamented bones of Discosaurixuc aumiacuc are mostly simple, but there are also more complicated, rarely serrated, sutures between some bones. In small individuals, the sutures are simple, but the same sutures also occur in the largest specimens. The character of the sutures and the incomplete ossification ofbones around the pineal foramen indicate the larva type of organization of DiKosauriKur The fenestra between premaxihies and nasals appears to be absent. In the majority of specimens, a squamosal-intertemporal sutural contact is present, altho~itissometimesredu~andinafewcasesintermptedbyapostorbitalandsupratemporal contact Therefore the character ‘intertmporal-squamosal suture present or absent’ cannot be used in this rigorous sense for testing the relationshipsof early tetrapods.The configuration of the suture between both parietals in osteolepiforms, Dixosaurixuc, and various early amphibians and reptiles indicates that the bones enclosing the pineal foramen in osteolepifonns are kontals. ODI~~RISCUS.Seymouriamorpha, Lower Permian mapod, skull woskLlcton, sutures. JoZqKlrmbara, Zoological Imthte, Faculty of Natural SCienceJ, Comeniuc University, Mlynskd dolina B-2,&42 15 Bratislava, Slovakia; 30th September, 1992; revised20th April, 1993. Two localities in the Boskovice Furrow in Moravia (Czech Material, methods and localities Republic) have produced a relatively large assemblage of more or less three-dimensional skeletal material of discosau- The localities and methods have been described by Klembara riscids (Klembara & MeszAroS 1992). Despite certain Mer- & MeszAroS (1992). ences in skull proportions, there are no reliable criteria for The following specimens (skull lengths 17-52 mm) were the determination of more than one species and genus used in this paper (D - locality DrvAlovice, K - locality (Klembara & Janiga 1993). In the following account, the new Kochov): D 18, D 47, D 52, D 69, D 70, D 87, D 208, K 1, K 13, collections of discosasuriscids from Moravia are interpreted K21,K3O,K41,K52,K72,KSO,K99,K 100,K 102,K 138, as one genus and species, Discosautisnrs ausrriacus (Makow- K 139, K 177, K 285, K 323, K 329, K 333, K 334, K 336. The sky 1876). specimens are deposited at Zoological Institute, Faculty of Discosauriscids are considered by most authors to be Natural Sciences, Comenius University, Bratislava. seymouriamorph tetrapods (e.g., Romer 1947; spinar 1952; Smithson 1985; Ivakhnenko 1987; Werneburg 1989), al- though an unambiguous assignment is not endorsed univer- Skull-roof bones sally (Heaton 1980; Holmes 1984). Detailed descriptions of the skull and the postcranial skel- In Discosaurixus, the dermal skull roof (Fig. 1) consists of all eton will be published in several papers, because this well- the bones normally present in seymouriamorph tetrapods preserved material deserves complete documentation.Many (e.g., Seymouria, White 1939, or Karpinskiosaurus, Ivakh- structures, in particular the sutures of the dermal skull roof, nenko 1987).There is a parietakabular contact, characteris- were previously undescribed. In some respects, this paper tic for Anthracosauria (sensu Save-Mderbergh 1934; 6. also complements the preceding paper (Klembara & Janiga Smithson 1985), one of the group of the reptiliomorph 1993) dealing with the proportional differences in Disco- evolutionary line of tetrapods (muSve-Merbergh 1934, SaUrisnrs. 1935; cf. Panchen & Smithson 1988). Unlike the embolo- The term ‘Anthracosauria’ will be used to include Embo- meres, but like Seymouria and Karpinskiosaurus and prob- lomeri, Gephyrostegidae and Eoherpetontidae (cf.‘Anthra- ablyalso Gqhyrostegus(Carrolll970) and Eoherpeton (Pan- cosauroideae’ sensu Smithson 1985). chen 1975), DiscosaurisncSpossesses a septomaxiUaxy. 86 Jozefk?embara LETHAL4 27 (1994) Fig 1. Discosauriscus aumiacus (Makowsky 18761, K 13. Skull in dorsal view. Abbreviations: FR - fiond, JU- jugal, IT - intertemporal,LA - lacrimal, MX - maxihy, NA - d,PA - paridPFR - prhond, PO - postorbid,POFR - postfrontal, PP - postparid, QJ- quadratojugal, SMX- septomaxihy, SQ - squamosal, ST - supratemporal,TA - tab*, tr.f. - transverse flange of pterygoid. Sutures position, or the orientation on a particular bone, is constant. An exception is the postparietal, in,which the median un- The sutures between the ornamented areas of the dermal ornamented area, which is overlapped by the other post- bones of the skull roof are almost always clearly visible. The parietal, is sometimes born by the left (e.g., K 177), and majority of the dermal skull-roof bones form squamose sometimes the right (e.g., D 47) postparietal. sutures, in which part of the edge of one bone overlaps the One of the simplest sutural patterns of the dermal skull unornamented part of the adjoining bone (e.g., parietals- roofofDiscosaurixusispresentinK13 (Fig. l).Theshapeof frontals, Fig. 1). In the region in front of the pineal foramen, the bone and its suture patterns are essentially bilaterally the nasals, hntals and parietals are closely attached at the symmetrical. The sutures between individual bones are midline, and the medial margin of one always fits to a certain simple. Such a ‘basic’ sutural pattern is relatively common degree into an elongated groove in the medial margin of the and does not depend on the size of the specimen. Diversity in other bone. In some skulls, however, these bones have rela- suture patterns is primarily the result ofvariations in size and tively broad unornamented areas (e.g., the left frontal of D shape of the ornamented surfaces, which is much more 87). Neither the lacrimal nor the maxillary form wider un- variable than the shape of individual bones. ornamented areas. The dorsal surface of the unornamented Because the detailed description of individual cranial areas is mostly markedly grooved (Fig. 1). Although the bones will be given in later papers, only the more pro- range of the unornamented areas can vary slightly, their nounced modifications of the relative positions of some LETHAIA 27 (1994) Skull-roof bones of DISCOSAURISCUS87 Fig. 2. Discosautiscusaustiacus (Makowdcy 1876). Skulls in dorsal view. ok K 138. OB. K 139. Abbreviations FR- frontal, IT - intertemporal,PA - parietal, PO - postorbital, POFR - postfrontal, ST - supratemporal. dermal bones and their ornamented surfaces regarding the bones is short (e.g., D 70 on the right) or fully interrupted condition in K 13 (Fig. 1) will be described here. (e.g., D 70 on the left); Fig. 4B. In some specimens (K 100, K 102, D 208), it is difficult to decide whether the contact was Region of the pineal foramen. - The size of the pineal fora- interrupted or not, because the distances involved are several men varies and does not depend on the size of the specimen. tenths of a millimetre. Moreover, the slight compression of In the majority of specimens, the pineal foramen is com- adjoining bones, often apparent at the junction of the skull pletely enclosed anteriorly by the parietal bones (Figs. 1,2A, table and cheek, may be of some importance. In K 333, 3B, 6). The length of the junction of the ornamented sur- however, a relatively long suture between the supratemporal faces of the parietals anterior to the pineal foramen varies. and postorbital (Fig. 5) completely precludes a squamosal- In some specimens this junction is relatively long (Fig. 2A), intertemporalcontact. This is due partly to a prolongation of but in others (e.g., D 18, K 139) the suture is not closed the posterior edge of the postorbital but mostly to the elon- anteriorly, and the frontal or fronds form part of its ante- gation of the anterolateral edge of the supratemporal (Figs. rior margin (Figs. 2B, 3A). Between the two extremes there 4B, 5). Although skulls show variability in relative width are many intermediate conditions (e.g., D 69, D 70, K 21, (Klembara & Janiga 1993), there is no correlation with the Figs. 3C, 4). This variation derives from the variable shape shorteningof the intertemporal-squamosal suture. A mini- of the anterior ends of the parietals and the posterior ends of mal junction ofthese bones, or its slight interruption, occurs the fiontals (on both right and left sides). As a result, differ- on ‘broad’, as well as ‘narrow’skulls (cf. specimen D 70, Fig. ent combinations of the character and length of the junc- 4B and Klembara & Janiga 1993, Fig. 1OC). It is also related tion of adjoining bones are produced, as well as variation in to the length of the postorbital bone, and/or its posterior the degree of participation of the frontal in the anterior process. It seems that individual variability is involved (cf. border of the pineal foramen. specimens D 69 and D 70, Figs. 4A and 4B). The position of the pineal foramen remains more or less constant; it varies only slightly relative to the anteroposterior Sutures beween the ornamented surfaces of bones. - The extent of the intertemporal. course of the sutures between the ornamented surfaces of individual skull-roof bones is rather variable, as is shown by Intertemporal-squamosul suture. - In the majority of skulls, theextentandshapeoftheseornamentedsurfaces.Thesecan the intertemporal has a lateral common suture with the besubstantidy different on the right and left side of the skull squamosal (Fig.