Sophineta cracoviensis Evans and Borsuk-Białynicka, 2009

Borsuk-Białynicka, Magdalena, 2018, Diversity of diapsid fifth metatarsals from the Lower Triassic karst deposits of Czatkowice, southern Poland - functional and phylogenetic implications, Acta Palaeontologica Polonica 63 (3), pp. 417-434 : 422

Sophineta cracoviensis Evans and Borsuk-Białynicka, 2009

Figs. 1C , 2C , 4A, B .

Material.—MttV: four complete specimens, ZPAL RV/1353, right ( Fig. 4B ); ZPAL RV/1990, left ( Fig. 4A ); ZPAL RV/1418, right; ZPAL RV/1999, right. Seven less complete unnumbered specimens. All from early late Olenekian, Czatkowice

, southern Poland.

Description.—The Sophineta cracoviensis MttV morphotype is the smallest of all, ranging from 3.5 to 5.0 mm

7 specimens), mostly about 4 mm in length, and very lepidosaurian in its strong inflection and hooking. The hooking angle is about 110°, but the orientation of the long axis of the shaft is difficult to determine in view of irregular shape of the latter ( Figs. 1C 1 , 4 ). The proximal articular facet is situated at the top of a well developed medial process, referred to as “articular neck” ( Fig. 1C 1 ) that protrudes mediad from the stem. The protrusion results in a strongly concave medial border and substantial asymmetry of the bone in dorsal aspect. The plantar surface is distinctly folded in transverse axis, A plantar convexity of the articular neck, that extends disto-laterally to about the midlength of the bone (a sort of roll-like eminence) and a proximo-distal furrow ( Fig. 4B 1 , C) that borders it laterally, both contribute to this folding. The facet for dTIV is oval, but closer to circular (the ratio ~1:1.4) than that in Osmolskina or morphotype X. The facet faces directly mediad and probably only contacted dTIV, allowing some flexion-extension movement. The inflection of the bone is strong ( Fig. 4B 2 ), which makes the dorsal face concave. This concavity is enhanced by a dorsal inclination of the outer process. Among the Czatkowice taxa, Sophineta is distinguished by a laterally convex lateral border. The lateral plantar tubercle covers the entire middle one third of the length of this border. It lies within a crest that invades the plantar surface and contributes to the medial twist of the bone shaft. The medial plantar tubercle is poorly developed and situated above the mid-length of the medial border. The distal end of the bone is twisted medio-plantar with respect to the proximal part and bears an articular facet for the first phalanx of the digit at its medial corner. The facet forms a short oval, its long axis oriented medio-lateral.

Stratigraphic and geographic range.— Early late Olenekian, Poland.

Figures

Fig. 1. Comparison of the fifth metatarsal architecture. Left bones in plantar view demonstrate hooking and articular facet orientation (A1–C1, D, E1, F1) and in proximal view (plantar surface down) (A2–C2, F2). A. Iguana iguana (Linnaeus, 1758), Iguanidae, Recent. B. Sphenodon punctatus (Gray, 1842), Rhynchocephalia, Recent.C. Sophineta cracoviensis Evans and Borsuk-Białynicka, 2009, Lepidosauromorpha, Early Triassic, Poland. D. Gephyrosaurus bridensis Evans, 1980, Rhynchocephalia, Early Jurassic, South Wales, UK (right MttV reversed). E. Osmolskina czatkowicensis Borsuk-Białynicka and Evans, 2003, Archosauriformes, Early Triassic, Poland. F. Morphotype X, Early Triassic, Poland. The dashed lines approximate the outlines of the fifth metatarsals as seen in proximal view (for additional explanation see Material and methods). ha, hooking angle. Not to scale. A, B1, C, after Robinson (1975); D, after Evans (1981).

Fig. 2. Comparison of fifth metatarsal architecture. Right bones in lateral view (A, B, C1, D, E2, F2) and in medial view (C2, E1, F1). A. Iguana iguana (Linnaeus, 1758), Iguanidae, Recent. B. Sphenodon punctatus (Gray, 1842), Rhynchocephalia, Recent. C. Sophineta cracoviensis Evans and Borsuk- Białynicka, 2009, Lepidosauromorpha, Early Triassic, Poland. D. Gephyrosaurus bridensis Evans, 1980, Rhynchocephalia, Early Jurassic, South Wales, UK; straight line approximates not-inflacted shape of the MttV. E. Morphotype X, Early Triassic, Poland (left MttV reversed). F. Osmolskina czatkowicensis Borsuk-Białynicka and Evans, 2003, Archosauriformes, Early Triassic, Poland. inf, inflection angle. Not to scale. A, B after Robinson (1975); D, after Evans (1981).

Fig. 4. Lepidosauromorph saurian Sophineta cracoviensis Evans and Borsuk-Białynicka, 2009 (A, B) and morphotype Y (C) from the Lower Triassic of Czatkowice, southern Poland and Macrocnemus bassani (Nopcsa, 1930) (D, E) from the Middle Triassic of Switzerland. A. ZPAL RV/1990, left MttV in dorsal (A1) and medial (A2) views. B. ZPAL RV/1353, right MttV in plantar (B1) and lateral (B2) views. C. ZPAL RV/1989, left MttV in plantar view. D. PIMZ T 2816, left MttV (reversed) in plantar view. E. PIMZ T 2472, right MttV in plantar view. A–C, SEM stereo-pairs. D, E not to scale, after Rieppel (1989: fig. 8B, E).