The pelvic girdle and hind limb ofCrassigyrinus scoticus(Lydekker) from the Scottish Carboniferous and the origin of the tetrapod pelvic skeleton

Abstract

Our knowledge of the primitive and aberrant early tetrapodCrassigyrinus scoticuswas based on a partial skull roof and mandibles from the Lower Carboniferous of Gilmerton, Edinburgh, plus a skeleton lacking the hind limb and tail from the Namurian, basal Upper Carboniferous, of Cowdenbeath, Fife. New specimens from Cowdenbeath include the pelvic girdle, presacral and sacral rib and most of the hind limb. The ilium of the girdle had a firm articulation with the vertebral column via the sacral rib. The ischium, separated from the ilium by cartilage, was, like that found with the Cowdenbeath skeleton, ornamented as though a dermal bone. No pubis is preserved. The femur lacks an adductor crest, but has a strongly developed internal trochanter. Tibia and fibula are short stout bones, but axial torsion is present in the fibula rather than the tibia. This, and the structure of the femur, suggests a swimming rather than a walking limb. Probable metatarsals and phalanges are recorded. A skeletal reconstruction and a life restoration ofCrassigyrinusare presented in the light of its reconstructed anatomy and physiology.The ornamentation of the ischium ofCrassigyrinus, and that of the colosteidGreererpeton, suggests that the bone may be at least in part dermal. Its homology wth the pelvic fin basal scute of osteolepiform fishes is proposed and the homologies of pectoral and pelvic fins, and thus limbs, discussed.

Postcranial remains of Baphetes and their bearing on the relationships of the Baphetidae (= Loxommatidae)

“…In lateral view, the ischium is flat and featureless with faint pits and ridges at the mid-point. Similar patterning was reported in CrasszgYrinus by Panchen (1985) and by Panchen & Smithson (1990) who likened it to dermal ornament and noted its presence also in O/eerereton, whereas Lebedev & Coates (1995) interpreted it as scars of caudal muscle insertions.…”

“…The mesial one-third of the proximal end is thus demarcated by a smooth flat-faced triangular facet extending distally about half the length of the bone. A similar triangular area is reported in CrusszgYrinus although it is in the form of a boss rather than a facet (Panchen & Smithson, 1990). The distal end of the tibia is convex in extensor view; in flexor view it is divided into distinct facets of equal size for the intermedium and tibiale.…”

“…The right ilium is almost complete and resembles those of Crms&yrinus (Panchen & Smithson, 1990), Acanthoskgu (Coates & Clack, 1995) and embolomeres in that it possesses both dorsal and posterior processes (Fig. 11).…”

The tetrapod Caerorhachis bairdi Holmes and Carroll from the Lower Carboniferous of Scotland

“…The proximal apex of the blade ends in a stout boss-like internal trochanter, separated from the proximal end of the femur by a deeply incised trough, a condition observed in e.g. Tulerpeton (Lebedev & Coates 1995), Crassigyrinus (Panchen & Smithson 1990) and Archeria (Romer 1957;Holmes 1989). A small, elongate tuberosity on the posterodorsal surface of the femoral head, lying approximately at the same transverse level as the internal trochanter, may represent the ischiotrochantericus muscle insertion, based on a comparison with a similarly positioned structure in the femur of the synapsid Dimetrodon (Romer 1956).…”

Reasonable classical concepts in human lower limb anatomy from the viewpoint of the primitive persistent sciatic artery and twisting human lower limb

“…Recently, Aizawa and Horiguchi (2000) suggested that the limbs might not have a homologue based on their positions and distributions of the cutaneous nerves in rat embryo. In addition, Panchen and Smithson (1990) suggested that the first mesomere of the pelvic fin of Eusthenopteron is the homologue of the second mesomere of the pectoral fin (i.e. Humerus is the homologue of Fibula).…”