ANGUINAE, Gray, 1825

Ivanov, Martin, Čerňanský, Andrej, Bonilla-Salomón, Isaac & Luján, Àngel Hernández, 2020, Early Miocene squamate assemblage from the Mokrá-Western Quarry (Czech Republic) and its palaeobiogeographical and palaeoenvironmental implications, Geodiversitas 42 (20), pp. 343-376 : 354-356

ANGUINAE indet.

( Fig. 6 F-K)

MATERIAL. — MWQ, early Miocene, Burdigalian, Orleanian, MN 4: 1/2001 Turtle Joint: one right and one left coronoid (Pal. 1408-1409), 38 osteoderms (Pal. 1410-1447); 2/2003 Reptile Joint: 374 osteoderms (Pal. 1577-1950).

DESCRIPTION

Coronoid

Both left and right coronoids are preserved, but the right one is in better condition. The element is a chevron shaped bone, with several major processes. The dorsal process, which is located in the mid-region, is shortest. However, it is a robust structure, slightly curved posteriorly. On the lateral side, the central region bears a ridge (or keel) for muscle attachment. The posterior process is broad. On its medial side, a strong muscular crest forms the anterior border of the adductor (mandibular) fossa. The whole posterior process is bent posteromedially and, in lateral aspect, the internal side has a wrinkled appearance (it is slightly sculpted by grooves). The anteromedial and anterolateral processes are incomplete. They are separated one from another by a well-developed notch. It shows that the coronoid process of the dentary overlapped this region. A wider base is present on the anteromedial process.

Osteoderms

The osteoderms are of two morphotypes. The first morphotype ( Fig. 6I, J ) is represented by a slender, flat, trapezoidal osteoderm. This type possesses a low medial ridge running along its entire central region, including both sculptured region and smooth overlap surface. The ornamentation is

formed by short ridges, tubercles and pits diverging from the central region. The sculptured region forms approximately 2/3 of the entire length of the osteoderm. The rest is formed by a smooth anterior overlap surface. The lateral bevel is highest close to the overlap surface. The central part of the internal surface is pierced by three foramina.

Osteoderms of the second morphotype ( Fig.6K ) are roughly rectangular in shape. This morphotype almost lacks the medial ridge – ornamentation is arranged only in the centre to form an indistinct ridge. This osteoderm type also differs from the first morphotype by its sculpture. It is denser because the ridges are broad, with narrow grooves between them. The smooth overlap surface is large. The internal surface is pierced by three foramina.

Figures

FIG. 6. — Ophisaurus and Anguinae indet. from the early Miocene (MN 4) of MWQ. Trunk vertebra Pal. 1407 (1/2001 Turtle Joint) of Ophisaurus sp. in (A) lateral, (B) dorsal, (C) ventral, (D) anterior and (E) posterior aspects. Anguinae indet.: right coronoid Pal. 1408 (1/2001 Turtle Joint) in (F) lateral, (G) medial and (H) dorsal aspects. Osteoderms Pal. 1577-1579 (2/2003 Reptile Joint) in (I-K) external aspects. Abbreviations: alp, anterolateral process; amp, anteromedial process; cd, condyle; ct, cotyle; dp, dorsal process; mr, medial ridge; muc, muscular crest; nc, neural canal; ns, neural spine; nt, notch; os, overlap surface; pof, postzygapophyseal articular facet; pp, posterior process; prf, prezygapophyseal articular facet; rd, ridge; scs, scupltured surface; syn, synapophysis. Scale bars: 2 mm.