Anatomical study of the skull of amphisbaenian Diplometopon zarudnyi (Squamata, Amphisbaenia)

Abstract

This study investigates the amphisbaenian species skull which includes cranium, lower jaw and hyoid apparatus. The medial dorsal bones comprise the premaxilla, nasal, frontal and parietal. The premaxilla carries a large medial tooth and two lateral ones. The nasals are paired bones and separated by longitudinal suture. Bones of circumorbital series are frontal, orbitosphenoid and maxilla. The occipital ring consists of basioccipital, supraoccipital and exooccipital. Supraoccipital and basioccipital are single bones while the exo-occipitals are paired. The bones of the palate comprise premaxilla, maxilla, septomaxilla, palatine, pterygoid, ectopterygoid, basisphenoid, parasphenoid, orbitosphenoid and laterosphenoid. Prevomer and pterygoid teeth are absent. Palatine represent by two separate bones. The temporal bones are clearly visible. The lower jaw consists of the dentary, articular, coronoid, supra-angular, angular and splenial. The hyoid apparatus is represented by a Y-shaped structure. The mandible is long and is suspended from the braincase via relatively short quadrate. There is an extensive contact between the long angular and the large triangular coronoid. Thus inter-mandibular joint is bridged completely by the angular and consequently, the lower jaws are relatively rigid and kinetic. The maxillae are suspended from the braincase largely by ligaments and muscles rather than through bony articulation. In conclusion, the skull shape affects feeding strategy in Diplometopon zarudnyi. The prey is ingested and transported via a rapid maxillary raking mechanism.

Keywords: Amphisbaenia; Diplometopon zarudnyi; Morphology; Skull; Squamata.

Fig. 1

X-ray photos of skull of Diplometopon zarudnyi show that the nasofrontal joint located in-between the frontal bones, nasal and the snout unit consists of the nasals, premaxillae, septomaxillae and vomer. (A) Dorsal view, (B) Ventral view, (C) Lateral view.

Fig. 2

Selected transverse sections (Tra) of Diplometopon zarudnyi skull. A, Tra001 Masson's trichrome, B, Tra002 PAS-Alcian blue, C, Tra003 bromophenol blue, D, Tra005 Masson's trichrome, E, Tra007 Masson's trichrome, F, Tra008 PAS-Alcian blue. X 40. d, dentary; dn, duct of naso-lacrymal; fr, frontal; mu, muscle; mx, maxilla; n, nasal; na, nasal anteroom; nc, nasal chamber; ng, nasal gland; nln, nervus lateralis nasi; nmn, nervus medialis nasi; pfr, prefrontal; pmx, premaxilla; smx, septomaxilla; snc, septum nasi cartilagineum; t, tooth; to, tongue.

Fig. 3

Selected transverse sections (Tra) of Diplometopon zarudnyi skull. A, Tra009 bromophenol blue, B, Tra011 Masson's trichrome, C, Tra013 Masson's trichrome, D, Tra014 PAS-Alcian blue, E, Tra015 bromophenol blue, F, Tra017 Masson's trichrome. X 40. dng, duct of nasal gland; jo, jacobson's organ; lng, lateral nasal gland; mt, maxillary tooth; pc, pulp cavity.

Fig. 4

Selected transverse sections (Tra) of Diplometopon zarudnyi skull. A, Tra019 Masson's trichrome, B, Tra023 Masson's trichrome, C, Tra024 Masson's trichrome, D, Tra025 Masson's trichrome, E, 027 H.E., F, Tra029 Masson's trichrome. X 40. aiaf, anterior inferior alveolar foramen; cf, conchal fold; dc, dentary canal; dnt, dentary tooth; p, parietal; slg, sublingual gland; tc, trabecula communis; tel, telencephalon; v, vomer.

Fig. 5

Selected transverse sections (Tra) of Diplometopon zarudnyi skull. A, Tra030 Masson's trichrome., X 40, B, Tra031 Masson's trichrome., X 40, C, Tra034 Masson's trichrome., X 40, D, Tra041 Azur., X 200, E, Tra037 Masson's trichrome., X 40, F, Tra043 Masson's trichrome., X 40. ang, angular; cb, ciliary body; chv, choanal vault; co, coronoid; ec, ectopterygoid; hg, harderian gland; l, lens; opc, optic capsule; os, orbitosphenoid; pal, palatine.

Fig. 6

Selected transverse sections (Tra) of Diplometopon zarudnyi skull. A, Tra049, B, 054, C, 056, D, 061, E, 062, F, 065. Masson's trichrome., X 40. cc, cranial cavity; mb, mixed bone; mc, meckelian canal; pbs, parabasisphenoid; sp, splenial.

Fig. 7

Selected transverse sections (Tra) of Diplometopon zarudnyi skull. A, Tra066, B, 068, C, 070, D, 075, E, 078, F, 082. Masson's trichrome., X 40. appr, alar process of prootic; exc, extracolumella; gf, gasserian foramen; pt, pterygoid; q, quadrate; sc, semicircular canal; vc, vidian canal.

Fig. 8

Selected transverse sections (Tra) of Diplometopon zarudnyi skull. A, Tra084, B, 085, C, 087, D, 094, E, 095, F, 100. Masson's trichrome., X 40. avsc, anterior vertical semi-circular canal; bo, basioccipital; c, columella; enc, endolymphatic canal; jr, jugular process; lsph, laterosphenoid; ooc, otic-occipital complex; otc, otic capsule; pas, processus ascendes of supraoccipital; pd, perilymphatic duct; pop, paraoccipital process; pro, prootic, rst, recessus scalae tympani; sq, squamosal; vb, vestibule.