Brain anatomy of two-toed sloth (Choloepus didactylus, Linnaeus, 1758): A comparative gross anatomical study of extant xenarthrans.

The neural system plays an important role in understanding some features of animals. Anatomical complexity correlates with the increase of functional capacity. Xenarthrans include anteaters (Vermilingua), armadillos (Cingulata) and sloths (Folivora). This group is the base of eutherian mammals, and understanding the anatomy of its neural system could provide data for functional and evolutionary interpretations. The gross anatomy of the xenarthran brain is recorded. Four extant families of Pilosa and two families of Cingulata were sampled. Usual dissection procedures were used, and the brains were analysed macroscopically. The brain of two-toed sloth, three-toed sloth, six-banded armadillo, giant anteater and collared anteater are gyrencephalic. Pygmy anteater, nine-banded armadillo, great long-nosed armadillo, southern naked-tailed armadillo and giant armadillo are lissencephalic. In most species, the rhinal fissure presents two segments, rostral and caudal (except in Vermilingua and three-toed sloth). The diencephalon and brainstem present similar anatomy. The cerebellum is wide and presents four lobes (rostral, central, caudal and floccular). Its average volume is 12.16% (Folivora), 14.26% (Vermilingua) and 18.61% (Cingulata). Among these groups, there is a statistical difference between Folivora/Cingulata concerning the cerebellum average. The general pattern of the brain of the xenarthrans is similar to that of other mammals.

Muscular anatomy of the pectoral girdle and forelimb of Iguana i. iguana (Squamata: Iguanidae) / Anatomia muscular do cíngulo peitoral e membro torácico de Iguana i. iguana (Squamata: Iguanidae)

Green iguana has arboreal and terrestrial habits. It is widely distributed in Central and South America, inhabiting several biomes in Brazil. Some researches were focused on this species, however, morphological information are still limited. With that in sight, we aimed to add data to the anatomical knowledge. Two post mortem specimen of Iguana i. iguana were acquired, donated by a scientific breeding, and dissected. To describe the muscles we refuted the skin and removed the fascias, individualizing the muscles. We identified the following muscles: pectoralis, deltoideus clavicularis, deltoideus scapularis, trapezius, latissimus dorsi, coracobrachialis brevis, coracobrachialis longus, serratus thoracis, levator scapulae, biceps brachii and triceps brachii. Some of them, like coracobrachialis brevis, present conservative anatomy, originating from the ventral surface of the coracoid and inserting onto the proximal humerus. Some, like trapezius and biceps brachii, are similar to other reptile species, trapezius takes its origin from the thoracodorsal fascia and biceps arises by two heads and inserts on the radial tuberosity. Deltoideus clavicularis and deltoideus scapularis share a common insertion tendon. Pectoralis varies its origin and divisions, however, the insertion always occur on the deltopectoral crest. Triceps brachii is comprised of four heads. Its long medial head originates via a tendinous arc, feature described only in crocodilians. We conclude that Iguana i. iguana forelimb musculature is similar to other reptiles, presenting its own characteristics that reflect its habits.

Iguanas verdes tem hábitos arbóreos, terrestres e aquáticos, e são totalmente herbívoras. Tem ampla distribuição na América Central e do Sul, habitando vários biomas no Brasil. Investigações diversas tiveram esta espécie como foco, embora informações morfológicas sejam ainda escassas. Objetivando adicionar dados ao conhecimento anatômico, dois espécimes de Iguana i. iguana foram obtidos post mortem, por doação de um criadouro científico, e dissecados. Os músculos foram individualizados para identificação e descrição das origens, inserções e características. Alguns músculos, como o coracobraquial curto, apresentam morfologia conservativa, sua origem ocorre na superfície ventral do coracóide e inserção na epífise proximal do úmero. O trapézio, o bíceps braquial e o deltóide clavicular se apresentam similares à outros répteis, com a origem do trapézio na fáscia toracodorsal e o bíceps, com duas cabeças, se inserindo no tubérculo do rádio. O deltóide clavicular possui o tendão de inserção unido ao do músculo deltóide escapular. O músculo peitoral apresenta variações em sua origem e divisões, mas a inserção sempre ocorre na crista deltopeitoral. A origem da cabeça longa caudal do tríceps ocorre por meio de arco tendíneo, característica antes descrita apenas em crocodilianos. A musculatura de Iguana i. iguana se apresenta similar à de outros répteis no geral, com características próprias refletindo seus hábitos.