Osteological Histology of the Pan‐Alcidae (Aves, Charadriiformes): Correlates of Wing‐Propelled Diving and Flightlessness

ABSTRACT
Although studies of osteological morphology, gross myology, myological histology, neuroanatomy, and wing‐scaling have all documented anatomical modifications associated with wing‐propelled diving, the osteohistological study of this highly derived method of locomotion has been limited to penguins. Herein we present the first osteohistological study of the derived forelimbs and hind limbs of wing‐propelled diving Pan‐Alcidae (Aves, Charadriiformes). In addition to detailing differences between wing‐propelled diving charadriiforms and nondiving charadriiforms, microstructural modifications to the humeri, ulnae and femora of extinct flightless pan‐alcids are contrasted with those of volant alcids. Histological thin‐sections of four species of pan‐alcids (Alca torda, †Alca grandis, †Pinguinus impennis, †Mancalla cedrosensis) and one outgroup charadriiform (Stercorarius longicaudus) were compared. The forelimb bones of wing‐propelled diving charadriiforms were found to have significantly thicker (∼22%) cortical bone walls. Additionally, as in penguins, the forelimbs of flightless pan‐alcids are found to be osteosclerotic. However, unlike the pattern documented in penguins that display thickened cortices in both forelimbs and hind limbs, the forelimb and hind limb elements of pan‐alcids display contrasting microstructural morphologies with thickened forelimb cortices and relatively thinner femoral cortices. Additionally, the identification of ...

Source: The Anatomical Record Part B: The New Anatomist - January 17, 2014 Category: Anatomy Authors: N. Adam Smith, Julia A. Clarke Tags: Cover Image Source Type: research