Abstract
The limbless skink Ophiomorus punctatissimus is a cryptozoic species found in the Peloponnese region of Greece and on the Greek island Kythira. To provide the first thorough description of the cranial and postcranial osteology of this species, both disarticulated specimens and X-ray computed tomographies of wet-preserved specimens were examined in detail. Resulting from this, an anatomical atlas of this species is provided. Two separate considerations, an evolutionary and an ecomorphological one, are made based on the observed adaptations related to limb loss in this skink. The structure of the girdles shows a particular pattern of reduction: whereas the pelvic girdle is mostly vestigial, the pectoral girdle is instead well developed, with all the elements typical of limbed lizards except for the actual limbs. This led us to hypothesize an asynchronous pattern of limb reduction during the evolution of this species, in which the hindlimbs regressed earlier than the forelimbs. Furthermore, considerations based on overall body morphology, osteology and the structure of the inner ear led to the recognition of this species as a burrowing ecomorph. In contrast to the morphology normally displayed in this ecomorph, O. punctatissimus is characterized by the retention of autotomic vertebrae in its tail. This is consistent with the habitats in which it lives, where active burrowing would be difficult because of the hard, rocky terrain. Instead, this skink hides among rocks on the surface and is, therefore, subject to greater predation risk.
Highlights
The scincid lizard genus Ophiomorus was first described by Duméril and Bibron (1839) to accommodate the species Ophiomorus miliaris Duméril and Bibron 1839, intended as a “junior objective synonym of Anguis punctatissimus” (Anderson and Leviton, 1966: 500, 525), which was subsequently renamed as Ophiomorus punctatissimus (Boulenger, 1887)
The limbless skink Ophiomorus punctatissimus is a cryptozoic species found in the Peloponnese region of Greece and on the Greek island Kythira
Following the first revision of the genus by Boulenger (1887), in which six species were recognized (Ophiomorus blanfordi, O. brevipes, O. latastii, O. persicus, O. punctatissimus, O. tridactylus), three more were added by Anderson and Leviton (1966): O. chernovi, O. raithmai and O. streeti
Summary
The scincid lizard genus Ophiomorus was first described by Duméril and Bibron (1839) to accommodate the species Ophiomorus miliaris Duméril and Bibron 1839, intended as a “junior objective synonym of Anguis punctatissimus” (Anderson and Leviton, 1966: 500, 525), which was subsequently renamed as Ophiomorus punctatissimus (Boulenger, 1887). In 2018, a twelfth species was described as O. kardesi Kornilios et al, 2018, to accommodate the Anatolian populations previously attributed to O. punctatissimus (Kornilios et al, 2018) The members of this skink genus are characterized by a strong tendency towards limb reduction, ranging from species having short limbs and a reduced number of fingers to completely limbless species. The genus shows two main adaptations: the western species group (O. latastii, O. persicus, O. punctatissimus) displays the greatest degree of limb reduction and adaptation to a life under rocks, whereas the eastern species group (O. blanfordi, O. brevipes, O. chernovi, O. raithmai, O. streeti, O. tridactylus, O. nuchalis) dwells in sand dune environments and has less reduced limbs (Anderson and Leviton, 1966). We tentatively further investigate the evolutionary history and adaptive significance of its limblessness
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