Osteology and Radiological Anatomy of the Thoracic Limbs of Temminck's Ground Pangolin (Smutsia temminckii).

Temminck's ground pangolin is the only pangolin present in South Africa. It is a myrmecophagous mammal with a bipedal gait. The thoracic limbs are used to break open ant nests, dig for food, and expand previously occupied burrows. This study describes the osteology and radiological anatomy of the thoracic limbs of this threatened species. Thoracic limbs from four Temminck's ground pangolins, which succumbed from electrocution or natural causes, were digitally radiographed in situ. The individual bones were then cleaned, described and digitally radiographed. The skeleton of the thoracic limbs revealed a similar number and arrangement of bones compared to that of domestic carnivores. The bones were robust and displayed numerous open epiphyseal lines. The latter provide an estimate of sexual maturity and should not be confused with fractures in injured ground pangolins. The scapula was broad and triangular-shaped. The humerus displayed a massive medial epicondyle. The radius and ulna were similarly sized, and displayed a broad radial trochlea and large olecranon tuber, respectively. The manus was composed of seven carpal bones, five short metacarpal bones and five digits of which the three central digits were the best developed. The unguicular process of the distal phalanx was bifid and elongated. The osteological characteristics indicate that the thoracic limbs of Temminck's ground pangolin are specifically adapted for protraction and retraction, strong elbow extension, flexion of the carpus and digits as well as pronation and supination of the antebrachium, as opposed to weight-bearing. These functions are likewise documented for other scratch-digging species. Anat Rec, 301:624-635, 2018. © 2017 Wiley Periodicals, Inc.

Bony Pits in the Ostrich (Struthio camelus) and Emu (Dromaius novaehollandiae) Bill Tip.

A specialized region of the bill tip characterized by a complex arrangement of mechanoreceptors and referred to as a bill tip organ, has been identified in numerous avians. A bill tip organ was initially inferred in kiwi species by the presence of numerous, bony pits in the rostrum of the bill, and later confirmed histologically. This study enumerates and compares the number and distribution of pits present in the bill tip in the ostrich and emu. The heads from 10 ostrich and 5 emu were prepared for osteological examination. The pattern and total number of pits was similar between the two species. However, the ostrich had significantly more pits in the regions underlying the Culmen and Gonys, whereas the emu displayed significantly more pits in the dorsal part of the mandibular rostrum. The relatively even distribution of pits in the inner and outer surfaces of both the mandibular and maxillary rostra suggest that the bill tip of the ostrich and emu are equally sensitive externally and intra-orally, as opposed to probing birds, where the major concentration of pits is located on the outer surfaces of the bill tips. The presence of pits in the bill tips of extant paleaognaths may be of relevance in interpreting the pits in the rostra of extinct therapod dinosaurs. The presence of bony pits in a region which is also well supplied with sensory nerves is highly suggestive of a bill tip organ in the ostrich and emu and which needs to be confirmed histologically. Anat Rec, 300:1705-1715, 2017. © 2017 Wiley Periodicals, Inc.

Morphological features of Herbst corpuscles in the oropharynx of the ostrich (Struthio camelus) and emu (Dromaius novaehollandiae).

The distribution of Herbst corpuscles in the oropharynx of the ostrich and emu has recently been documented. However, although the morphology of these mechanoreceptors is well known in neognathous birds, little structural information is available on the Herbst corpuscles of ratites. Tissue sections from those regions of the oropharynx known to possess a high concentration of Herbst corpuscles were sampled from ostrich and emu heads collected after slaughter and prepared for light and transmission electron microscopy. Intra-oral Herbst corpuscles in the ostrich and emu displayed the same basic components (capsule, outer zone, inner core and axon) described in neognathous birds. However, some important differences were observed, notably, the presence of myofibroblasts in the capsule, sensory cilia in cells of the outer layers, a relatively larger, less organized outer zone and narrower inner core, and variations in the shape of the axon. The previously unreported presence of myofibroblasts in the capsule possibly indicates its ability to contract, thus altering the tension of the capsule, which in turn has implications for the conduction of vibrational stimuli. The sensory cilia in the myofibroblasts of the capsule bordering the outer zone, and in the fibroblasts of the outer zone itself, may play a regulatory role in controlling the contraction of the capsule. Such a function has not previously been reported for Herbst corpuscles in any species of bird.

Evidence of a true pharyngeal tonsil in birds: a novel lymphoid organ in Dromaius novaehollandiae and Struthio camelus (Palaeognathae).

BACKGROUND: Tonsils are secondary lymphoid organs located in the naso- and oropharynx of most mammalian species. Most tonsils are characterised by crypts surrounded by dense lymphoid tissue. However, tonsils without crypts have also been recognised. Gut-associated lymphoid tissue (GALT), although not well-organised and lacking tonsillar crypts, is abundant in the avian oropharynx and has been referred to as the "pharyngeal tonsil". In this context the pharyngeal folds present in the oropharynx of ratites have erroneously been named the pharyngeal tonsils. This study distinguishes between the different types and arrangements of lymphoid tissue in the pharyngeal region of D. novaehollandiae and S. camelus and demonstrates that both species possess a true pharyngeal tonsil which fits the classical definition of tonsils in mammals. RESULTS: The pharyngeal tonsil (Tonsilla pharyngea) of D. novaehollandiae was located on the dorsal free surface of the pharyngeal folds and covered by a small caudo-lateral extension of the folds whereas in S. camelus the tonsil was similarly located on the dorsal surface of the pharyngeal folds but was positioned retropharyngeally and encapsulated by loose connective tissue. The pharyngeal tonsil in both species was composed of lymph nodules, inter-nodular lymphoid tissue, mucus glands, crypts and intervening connective tissue septa. In S. camelus a shallow tonsillar sinus was present. Aggregated lymph nodules and inter-nodular lymphoid tissue was associated with the mucus glands on the ventral surface of the pharyngeal folds in both species and represented the Lymphonoduli pharyngeales. Similar lymphoid tissue, but more densely packed and situated directly below the epithelium, was present on the dorsal, free surface of the pharyngeal folds and represented a small, non-follicular tonsil. CONCLUSIONS: The follicular pharyngeal tonsils in D. novaehollandiae and S. camelus are distinct from the pharyngeal folds in these species and perfectly fit the classical mammalian definition of pharyngeal tonsils. The presence of a true pharyngeal tonsil differentiates these two ratite species from other known avian species where similar structures have not been described. The pharyngeal tonsils in these ratites may pose a suitable and easily accessible site for immune response surveillance as indicated by swelling and inflammation of the tonsillar tissue and pharyngeal folds. This would be facilitated by the fact that the heads of these commercially slaughtered ratites are discarded, thus sampling at these sites would not result in financial losses.

What prevents Struthio camelus and Dromaius novaehollandiae (Palaeognathae) from choking? A novel anatomical mechanism in ratites, the linguo-laryngeal apparatus.

BACKGROUND: The avian glottis channels air from the oropharynx to the trachea and is situated on an elevated structure, the laryngeal mound. It is imperative that the glottis be protected and closed during swallowing, which in mammals is achieved by covering the glottis with the epiglottis, as well as by adduction of the arytenoid cartilages. An epiglottis, however, is reportedly absent in birds. Ratites such as Struthio camelus and Dromaius novaehollandiae possess a very wide glottis in comparison to other birds. The question therefore arises as to how these large birds avoid inhalation of ingesta through a wide glottis, with apparently little protection, particularly as their feeding method involves throwing the food over the glottis to land in the proximal esophagus. RESULTS: In S. camelus when the glottis was closed and the tongue body retracted, the smooth tongue root became highly folded and the rostral portion of the laryngeal mound was encased by the pocket in the base of the ∩ - shaped tongue body. In this position the lingual papillae also hooked over the most rostral laryngeal projections. However, in D. novaehollandiae, retraction of the tongue body over the closed glottis resulted in the prominent, triangular tongue root sliding over the rostral portion of the laryngeal mound. In both S. camelus and D. novaehollandiae these actions resulted in the rostral portion of the laryngeal mound and weakest point of the adducted glottis being enclosed and stabilised. CONCLUSIONS: Only after conducting a comparative study between these two birds using fresh specimens did it become clear how specific morphological peculiarities were perfectly specialised to assist in the closure and protection of the wide glottis. We identify, describe and propose a unique anatomical mechanism in ratites, which may functionally replace an epiglottis; the linguo-laryngeal apparatus.