Kinelia broomi Bulanov, 2002

Säilä, Laura K., 2009, Alpha taxonomy of the Russian Permian procolophonoid reptiles, Acta Palaeontologica Polonica 54 (4), pp. 599-608 : 603-605

Kinelia broomi Bulanov, 2002

Figs. 4 , 5 .

Holotype and only specimen: PIN 4538 /3, a fragmentary right dentary.

Type locality: Vozdvizehnka, Russia.

Type horizon: Kutlukskaya Svita, Vyatkian Gorizont (uppermost Tatarian).

Diagnosis.—Extremely small tetrapod, possibly a parareptile, Kinelia is differentiated from other known tetrapod taxa by: (1) tightly packed teeth with labiolingually expanded tooth bases and labially situated tooth apices, set within a dental groove by subpleurodont tooth attachment, and (2) an oval symphyseal facet.

Remarks.—In the original description of Kinelia, Bulanov (2002) indicated that the length of the dentary was approximately 15 mm, which is almost double its actual length.

Description.—The dentary of Kinelia is minuscule, only 8.2 mm long, but because it is broken at its distal end, it must have been somewhat longer in life ( Fig. 4 ). Bulanov (2002) called the dentary “massive” but it is in fact quite narrow, with the teeth being about the same height as the dentary bone in medial view ( Figs. 4A , 5A ). A deep Meckelian facet secondary bone groove, a facet for the attachment of the splenial and a transversely oval symphyseal facet are also visible on the medial side ( Figs. 4A , 5A ).

The teeth of Kinelia appeared to be individually ankylosed to the bone in the drawings of Bulanov (2002: fig. 3) but this is not the case. There is in fact a deep groove, with a higher labial wall, in which the teeth are sitting ( Figs. 4 , 5 ). Between the teeth and the lingual wall, and between the individual teeth, is a mass of porous bony substance, which is interpreted as secondary bone for tooth attachment ( Fig. 5A, B ). It is impossible to see if the teeth have roots or sockets within the dental groove, but the existence of the secondary bone, covering the tooth bases and attaching the teeth to the dental groove, implies that no roots were present and that the type of tooth attachment is “subpleurodont”, a subtype of pleurodonty where tooth bases are extensively covered by bone of attachment ( Presch 1974; Motani 1997). The illustrations of Bulanov (2002) imply there is a tooth pit/alveolus where the ninth tooth is missing, but the space within the dental groove here is actually filled with sediment that should be carefully removed to expose this area for study.

There are ten teeth on the dentary, and an indication of at least one more tooth, but several more could have been present. The first tooth is the smallest, and although its base is somewhat transversely broadened, it has a slightly conical shape with a concave posterior surface and a sharp tip ( Fig. 5A–D ). The size of the third tooth suggests that the teeth are successively taller until the sixth tooth, and possibly even further posteriorly, but this cannot be determined in the posteriormost teeth because the crowns have been damaged. In occlusal view, the teeth become slightly smaller in basal cross−section posteriorly. On each of the third, fifth and sixth teeth, where the crown is intact, the tip is transversely flattened and has moved into a position toward the lateral margin of the jaw ( Fig. 5B ). The teeth are also highly convex on their lingual side leading to the tip and concave on the labial side below the tip. This is most evident when the teeth are viewed from a position posterior to the tooth row ( Fig. 5D ).

Comments.— Bulanov (2002) assigned Kinelia to Procolophonoidea , and more specifically to the Subfamily Spondylolestinae , based on the pronounced size−heterodonty of the anterior dentition. However, size−heterodonty of teeth is not something limited to procolophonoids and, for example, the parareptile Macroleter poezicus Tverdokhlebova and Ivakhnenko, 1984 from the Russian Permian has a dentition that is variable in size along the tooth row ( Tsuji 2006). Furthermore, Spondylolestinae is not considered a valid clade anymore and Spondylolestes is possibly a nomen dubium (Spencer 2000; Spencer and Benton 2000; Modesto et al. 2001). Cisneros (2008a), on the other hand, considered Kinelia a procolophonid because it has transversely broadened teeth. Again, however, procolophonids are not the only contemporaneous group with transversely broadened teeth. Trilophosaurids (archosauromorph diapsids), the parareptile Belebey and many synapsids from the Permo−Triassic have transversely broadened dentition ( Sues and Olsen 1993; Spencer and Benton 2000; Reisz et al. 2007). However, the dentition of Kinelia does, on a superficial level, resemble the dentition of derived procolophonids more than it resembles the dentition of any of other groups with transversely broadened dentition. The main difference, however, is the tooth attachment type. Recently, Vitalia grata Ivakhnenko, 1973 and Coelodontognathus donensis Otshev, 1967 , Triassic reptiles from Russia with transversely broadened dentition, were excluded from Procolophonoidea by Spencer and Benton (2000) because they lack procolophonoid features. One of the differences between procolophonoids on the one hand and Vitalia and Coelodontognathus on the other is that the latter taxa both have very deep tooth roots (this can be clearly seen on PIN 4173/126, PIN 1043/628, and PIN 4173/127–128), a dental attachment type not found in any procolophonoid. These two taxa have now been tentatively reclassified as trilophosaurids ( Arkhangelskii and Sennikov 2008) on the basis of tooth shape. Similarly, the subpleurodont dental attachment type of Kinelia is not known in procolophonoids.

Furthermore, the actual teeth of Kinelia are different from those of any procolophonoid. Owenettids have a conical dentition and many derived procolophonids have transversely broadened teeth, usually with two cusps on each tooth. Contritosaurus and Phaanthosaurus (which are regarded as synonyms by Spencer and Benton 2000), however, do have transversely broad tooth bases with only one cusp but there are many features on the dentition of Kinelia that differ from Contritosaurus, Phaantosaurus , and other procolophonoids. Most procolophonids, including Phaanthosaurus (PIN 1025/1), have a number of tall, conical caniniform teeth at the anterior end of the dentary, and even if there is a reduction in number, the remaining single caniniform tooth is massive in size (for example in Hypsognathus, Sues et al. 2000 ). In Kinelia , however, the first tooth is the smallest and shortest of all the preserved teeth. The following teeth are transversely expanded, and while the shape of the tooth bases is quite similar to those of the maxillary dentition of Contritosaurus convector ( Fig. 3C ), the crowns are unlike those of any procolophonid with their labially situated, flattened tips and the convex lingual and concave labial sides ( Fig. 5B–D ).

Of the badly broken dentary bone itself, the facet for the splenial is situated around the same region in Kinelia ( Fig. 5A ) as in procolophonids, but the oval symphyseal facet, situated just underneath the tooth−bearing ramus, is very different from the extensive renal−shaped facet of Phaantosaurus (PIN 1025/1), Procolophon ( Carroll and Lindsay 1985) and Leptopleuron (BMNH R3931), that covers the whole anterior tip of the dentary. Thus, Kinelia displays many features that support its exclusion from, and none that would unequivocally support its inclusion in, Procolophonoidea . Kinelia is therefore considered Tetrapoda incertae sedis, although it clearly represents a valid taxon with unique autapomorphies. It could be a non−procolophonoid parareptile but this classification is uncertain because of the limited material.

Stratigraphic and geographic range.—Vyatkian (uppermost Tatarian) of European Russia.

Excluded taxa Microphon exiguus Ivakhnenko, 1983

Figs. 6 , 7 .

Microphon exiguus , from the Upper Permian (Tatarian) of Russia, was long considered the earliest record of Procolophonidae ( Ivakhnenko 1983; Spencer and Benton 2000; Modesto et al. 2001). Bulanov (2002), however, excluded Microphon from Procolophonoidea after reidentifying it as a seymouriamorph, and confirmed this in an extensive review of seymouriamorphs that includes many illustrations of paratypes referable to the species M. exiguus and the genus Microphon , previously assigned to the genera Raphanodon or Raphaniscus ( Bulanov 2003) . However, the holotype of M. exiguus, PIN 3585/31, was the only specimen illustrated by Ivakhnenko (1983) and Bulanov (2002), and both papers featured only line drawings that differ from each other considerably. Furthermore, the seymouriamorph review of Bulanov (2003) also only has a reconstructive drawing of the holotype specimen, again somewhat different from previous drawings, leaving it unclear what the holotype actually looks like and whether it is comparable to the seymouriamorph specimens included in the genus. Photographs, accompanied by line drawings, are provided here to clarify the affinities of this specimen ( Figs. 6 , 7 ).

The holotype specimen, PIN 3538/31, is an isolated maxilla, and the anterior end of the specimen was at some point broken off and subsequently glued back in the wrong position, with the marginal teeth pointing medially ( Figs. 6 , 7A, C ). This erroneous orientation of the anterior part of the maxilla causes the anterior extension of the tooth shelf, which should be pointing horizontally on the medial side, to be visible in lateral view and was illustrated by Ivakhnenko (1983: fig. 1), where it appears similar to the “maxillary depression” of procolophonids. Bulanov (2002) pointed out this mistake and illustrated the anterior part of the maxilla in a more true orientation, but even his depiction ( Bulanov 2002: fig. 1) is not entirely correct when compared to how the maxilla would look with the anterior end in its true orientation ( Fig. 7B ).

Ivakhnenko’s (1983) illustration also depicts the maxilla as having a large foramen behind the “maxillary depression”, another feature found in procolophonoids (and several other parareptiles), but this foramen is absent in the illustrations of Bulanov (2002, 2003). The specimen, in fact, has a hole in this location but this has an unnatural shape and does not continue into the bone ( Fig. 7A ). This “foramen” was caused by damage during preparation (Valery Bulanov, personal communication 2006), a fact supported by the damage around the “foramen”, and was left out of the illustrations of Bulanov (2002, 2003) for this reason. In other respects, the drawings of Bulanov (2002, 2003) are fairly accurate and illustrate the clearly pleurodont dentition, the numerous foramina on the medial side and the pitted surface of the lateral side that can be seen on the specimen ( Fig. 7 ). These are all compatible with the identification of Microphon as a seymouriamorph ( Bulanov 2002, 2003), and additional material, consisting of well−preserved cranial remains, confirms this ( Bulanov 2003).

Figures

Fig. 4. Tetrapod Kinelia broomi Novikov 2002, Kutlukskaya Svita, uppermost Tatarian; PIN 4538/3 (holotype), partial right dentary. In medial (A) and lateral (B) views.

Fig. 5. Tetrapod Kinelia broomi Novikov 2002, Kutlukskaya Svita, uppermost Tatarian; PIN 4538/3 (holotype), partial right dentary. In medial (A), occlusal (B), and lateral (C) views. D. Schematic representation of the four well−preserved tooth crowns of the dentary teeth from posterior view. Lingual to the right, not to scale.

Fig. 3. Procolophonid reptile Contritosaurus convector Ivakhnenko 1974, Vokhmian Gorizont, Induan, earliest Triassic; PIN 3357/2, partial right maxilla. In lateral (A), medial (B), and occlusal (C) views.

Fig. 6. Seymouriamorph Microphon exiguus Ivakhnenko, 1983, Severodvinian Gorizont, Tatarian; PIN 3585/31 (holotype), right maxilla, in lateral (A) and medial (B) views.

Fig. 7. Seymouriamorph Microphon exiguus Ivakhnenko, 1983, Severodvinian Gorizont, Tatarian; PIN 3585/31 (holotype), right maxilla, in lateral view (A), lateral view of the anterior end (B; attached to the maxilla incorrectly in A), and medial view (C).