Sarcopterygii, Romer, 1955
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publication ID |
https://doi.org/ 10.4202/app.01044.2022 |
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persistent identifier |
https://treatment.plazi.org/id/5917A15C-2E2F-FFBE-FCE2-FE2FCB8D672D |
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treatment provided by |
Felipe |
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scientific name |
Sarcopterygii |
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Sarcopterygii indet.
Fig. 7–9 View Fig View Fig View Fig .
Material.—MZ-VIII/Vp-66, 401–403, 437, 449, 457, 581, PIG-PIB-2P, 3P, 4P 12P, PIG 273, 349, PIG 1733.II.437, D1080aD27UW, parts of the skull and postcranial skeleton; Podłazie, Emsian ( Kulczycki 1960: pl. 6: 16).
Description.— Jugal: MZ-VIII/Vp-581 was microtomographically studied ( Fig. 7 View Fig ). It consists of an isolated right jugal (20 mm long and 12 mm high), relatively well preserved although the straight lower margin, which contacted the maxilla, appears to be slightly eroded, however, its course is easy to trace ( Fig. 7A View Fig 1 View Fig , A 3 View Fig ). The jugal is exter- nally convex and gently concave viscerally ( Fig. 7A View Fig 5 View Fig ). All the contacts with the other cheek bones are well recogniz- able ( Fig. 7A View Fig 6 View Fig ). The anterior margin, which contacted the lachrymal, is pierced by an opening for the jugal sensory canal that runs across the bone ( Fig. 7A View Fig 1 –A View Fig 5 View Fig ). The orbit rim is deeply concave and is antero-dorsally located. The postero-dorsal margin is slightly concave and would have contacted the postorbital. Across this margin, a double infraorbital sensory canal opening is visible. Both openings are closely located and separated by a thin septum of about 2 mm in thickness, however may represent secondary structure among ramification of the main canal ( Fig. 7A View Fig 2 View Fig , A 3 View Fig , A 5 View Fig ). The posterior margin is straight for the contact with the squamosal and it carries an opening for the infraorbital sensory canal, visible in posterior view. The course of the lateral line canals can be followed on the visceral side through elongated thickenings revealing a relatively straight infraorbital canal running close to the ventral margin and the junction between the postorbital branch and infraorbital lateral line canals on the postero-ventral corner of the bone. Due to the poor preservation there are no visible pores or other evidences of cosmine.
Lower jaw: Six incomplete lower jaws (MZ-VIII/Vp- 401–403, PIG-PIB-2P, PIG 349, PIG 1733.II.437) have been found ( Fig. 8A–F View Fig ). Some of these specimens (MZ-VIII/ Vp-401–403, PIG 1733.II.437) were briefly described by Dec (2010). The smallest specimen (PIG-PIB-2P, Fig. 8A View Fig ) is 24 mm long and 5 mm high and corresponds to an incomplete dentary. On the external surface, the small pores of the cosmine cover are visible. The small specimen MZ-VIII/ Vp-401 (28 mm in length, Fig. 8B View Fig ) preserves the symphysis anteriorly and the lamina carrying the parasymphysial dental plate is also visible. PIG 349 ( Fig. 8C View Fig ) is 36 mm long. On the upper edge the row of six tooth sockets is visible. The external surface is covered with cosmine, but the inner side is smooth without any characteristics. MZ-VIII/Vp- 402 ( Fig. 8D View Fig ) is preserved from both, visceral and outer side. The 60 mm long external part is preserved to a greater extent, whereas only 20 mm of the visceral side are visible. The external surface on the specimen is covered with cosmine. On the visceral side a part of coronoid without a coronoid fang is preserved. On the external surface of MZ-VIII/ Vp-403 (51 mm long) which is covered with cosmine, the pore arrangement of the lateral line network is visible ( Fig. 8E View Fig ). Due to partial damage to the bone, the top layer on the posterior part of the specimen has been breached so it is possible to track the main lateral line canal with short branches extending from it. PIG 1733.II.437 ( Fig. 8F View Fig ) represents the anterior tip of a toothless lower jaw but it is very eroded and poorly preserved.
Maxilla: Two maxillary fragments (MZ-VIII/Vp-449, PIG-PIB-3P), have been found. MZ-VIII/Vp-449 ( Fig. 8G View Fig ) is rectangular in outline and it is about 60 mm long and 40 mm wide. The entire external surface is covered with cosmine pores. One little tooth is preserved with only its tip visible in lateral view. Most likely the specimen represents the middle part of the maxilla. Specimen PIG-PIB-3P ( Fig. 8H View Fig ) is almost 90 mm long and 20 mm wide. It displays three little teeth and a visceral ridge visible on the lingual side.
Ethmosphenoid: MZ-VIII/Vp-437 ( Fig. 9A View Fig ) is 25 mm wide and 17 mm high. The internasal cavities are bean shape with a noticeable internasal ridge. The floor of the left internasal cavity is broken. The area for the right vomer is slightly marked on the outer margin of the right internasal cavity, but it is also incomplete. A portion of the premaxilla bearing six tooth sockets is visible on the anterior margin of the specimen.
Postparietal and tabular: An incomplete left part of a postparietal (PIG-PIB-12P, Fig. 9B View Fig ) is 77 mm long and 39 mm wide. Only the dorsal surface is visible. The overlapping surface for the tabular is observed on the lateral side, which is located deeper in comparison to the external surface of the postparietal. The medial edge is badly preserved. The posterior margin is almost complete, it displays a slightly sinusoid contour. The tabular is 42 mm long and 19 mm wide. The outer margin appears to be eroded on the anterolateral and bottom edge.
Other elements: The general outline of D1080aD27UW Fig. 9C View Fig ) is triangular in shape and broad-base. It is 5.2 cm long and 4 cm in the widest point. All the outer surface is ornamented. MZ-VIII/Vp-66 ( Fig. 9G View Fig ) similar to the previous specimen, triangular in shape is 4.8 cm long and 2.3 cm in the widest point, it has been presented by Kulczycki (1960: pl. 6: 16). Its external surface is also ornamented. Specimen PIG 273 ( Fig. 9D View Fig ) is a dermal bone covered entirely with cosmine. The anterolateral margin is slightly lower and has no cosmine cover, which indicates that another bone was overlapping it. There is no visible lateral line canal. The specimen is 4 cm long and 2.5 cm wide. The last one is MZ-VIII/Vp-457 ( Fig. 9F View Fig ). It is 4.9 cm long and 3.2 cm wide, tapering to one extreme. Both external side edges are broken, however, one part has a deep, oval depression for overlapping bone. The dorsal edge of the bone is covered by little cavities.
Remarks.—The isolated jugal bone displays a series of pe- culiar features. The shape of the orbital margin suggests relatively large eyes. The bone contacted certainly the lachrymal, maxilla, squamosal and postorbital and postero-ventrally framed the orbit ( Fig. 7A View Fig 1 View Fig ). This general arrangement fits the condition known in porolepiforms (e.g., Mondéjar-Fernández 2020: fig. 10), onychodonts ( Mondéjar-Fernández 2020: fig. 17), “osteolepiforms” ( Jarvik 1985: figs. 2C, 5A–C; Borgen 2011: fig. 143D, J; Borgen and Nakrem 2016: fig. 143D, J) and other tetrapodomorphs
Säve-Söderbergh 1932: text-figs. 2, 11, 12, 15; Jarvik 1996: figs. 23, 24; Daeschler et al. 2009: fig. 4A, B). However, the bone is proportionally short with a relatively large and concave orbital margin, different from porolepiforms like Porolepis brevis , Nasogaluakus chorni , Laccognathus panderi , and Durialepis edentatus ( Jarvik 1972: fig. 43C; Schultze 2000: fig. 4; Mondéjar-Fernández and Clément 2012: fig. 11; Mondéjar-Fernández 2020: fig. 10) in which the jugal is relatively large and the orbital margin being comparatively shorter. Moreover, the length of each margin is almost equal in this specimen, whereas in porolepiforms the largest edges are those for the postorbital and maxilla e.g., Jarvik 1972: fig. 5; Mondéjar-Fernández 2020: figs. 9, 10; Mondéjar-Fernández and Clément 2012: fig. 11). The specimen of Porolepis brevis described and illustrated by Jarvik (1972: pl. 6: 1) has a jugal bone with outline shape and proportions similar to the Polish specimens. However, if the position in Jarvik’s figure (1972: pl. 6: 1) is rotated the margin which contacts the maxilla includes the posterior opening of the jugal sensory canal, which is obviously incorrect. A very short orbital rim or no contact whatsoever between the orbit and the jugal occurs in “osteolepiforms”. Despite the fact that the relative length of the bone margins and general shape of the jugal in certain “osteolepiforms” like Gyroptychius ( Jarvik 1985: fig. 5) are similar to this Polish specimen, the extremely reduced contact between the jugal and the orbit strongly differs. Comparisons with onychodonts do not allow to assign the specimen to this group. The jugal in onychodonts does not show a concaved eye margin and is rather straight (e.g., Andrews et al. 2006: figs. 3B, 4B; Long 2001: fig. 1). The jugal in onychodonts also possesses an overlapping surface for the lachrymal in the anterior part, which is not present in the Polish specimen. Among onychodonts, Onychodus sp. displays a ventral expansion of the infraorbital sensory canal into maxilla ( Long 2001: fig. 1C), which also does not occur in the Polish specimen. Because of its unusual proportions that suggest the presence of large orbits, this jugal bone does not fit to any known taxa already identified in the “Placoderm Sandstone”. The posterior part of the bone and the anterior margin for the contact with the lachrymal suggest a robust maxilla with anteriorly high portion forming a triangle pointing towards the jugal–lachrymal suture; this feature is similar to that of the tetrapod Ichthyostega sp. ( Ahlberg et al. 2005). Other features may also point towards a tetrapodomorph affinity of this bone. Daeschler et al. (2009: fig. 4A, B) illustrated two jugal plates belonging to undetermined tetrapod forms. They are similar to the specimen from Podłazie in carrying deeply concave orbital margins, especially in ANSP 22892 ( Daeschler et al. 2009: fig. 4B), but the contact with the maxilla is significantly shorter in the Polish specimen. The plate seems not to be abraded as it preserves almost all of its natural margins. On the inner side, elongated elevations reveal the course of the lateral line canal. However, the external side does not show any signs of the course of the lateral line, suggesting that it was deeply enclosed in the bone and pores on the surface are unfortunately not visible due to the scan resolution. Enclosing of the retained lateral line is regarded as an advanced character of the tetrapodomorphs (e.g., Ahlberg and Milner 1994; Jarvik 1996; Clack 2012). To sum up, a precise identification of the specimen is not possible because of its preservation as an isolated element. However, based on comparisons with other putative co-eval sarcopterygian candidates, it most likely represents an undetermined tetrapodomorph form.
Described here lower jaws (MZ-VIII/Vp-401–403, PIG- PIB-2P, PIG 349, PIG 1733.II.437) are either too damaged or solely preserved on one side without any distinctive characters that allowed identifying any taxa in detail. However, the presence of cosmine on the external side of the dermal bones allows to assign them to Sarcopterygii (except Actinistia and Onychodontida ; Schultze 2016).
MZ-VIII/Vp-449 and PIG-PIB-3P most likely represent parts of maxilla ( Mondéjar-Fernández 2020: figs. 5, 6) of porolepiforms owing to the shape (long and narrow) and the presence of big pores on cosmine cover.
The ethmosphenoid MZ-VIII/Vp-437 ( Fig. 9A View Fig ) is completely different from those known in the “ Porolepididae ” and presented herein ( Fig. 2 View Fig ). A rather thin internasal ridge and rounded, bean-shape internasal cavities were not observed in any known species. In most porolepiforms, the internasal cavities are rounded ( Porolepis cf. spitsbergensis, Jarvik, 1972 [pl. 7: 1]; Powichthys thorsteinssoni, Jessen, 1980 [pl. 5: 1], oval ( Porolepis brevis, Jarvik, 1972 [fig. 65]; Glyptolepis groenlandica, Jarvik, 1972 [fig. 31]) whereas they are more elongated in onychodonts, e.g., Qingmenodus yui Lu and Zhu, 2010 ( Lu et al. 2016: fig. 1A).
PIG-PIB-12P ( Fig. 9B View Fig ) shows a postparietal and tabular which are similar to Glyptolepis groenlandica ( Mondéjar-Fernández 2020: fig. 10H). The general outline of the described specimen is almost the same but the upper part of the postparietal is more “sinusoidal” than it is in Glyptolepis . The notch for the tabular also shows resemblance to Glyptolepis , however, due to the fact that the major part of the tabular is eroded it is hard to estimate the approximated natural shape of the bone.
Among the dozens of disarticulated remains, several bones can only be assigned to the osteichthyans ( Fig. 9C– G View Fig ). Some bones described herein as “other elements” belong most likely to Sarcopterygii but due to the state of the preservation they cannot be determined accurately. Only those that have cosmine (PIG-273, MZ-VIII/Vp-457) could be tentatively assigned to porolepiforms but cosmine is also present in basal tetrapodomorphs and dipnoans. PIG-PIB-4P ( Fig. 9E View Fig ), which probably represents urohyal has a wide anterior end, narrowing greatly towards the posterior end, thus more closely resembling the one in Eusthenopteron foordi ( Jarvik, 1954 [fig. 10D]). D1080aD27UW has a very spe- cific ornamentation, which is similar to the one occurring in Eusthenodon bourdoni ( Downs, Barbosa, and Daeschler, 2021 [fig. 6]). MZ-VIII/Vp-66 has a similar ornamentation, and these characters can indicate a potential affinity to Eusthenodon sp. MZ-VIII/Vp-66 could possibly correspond to the anterior part of a clavicle (e.g., Downs et al. 2018: fig. 7B) but due to the poor state of preservation is hard to establish with any certainty.
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