Bone and muscular anatomy of the forearm and hand in Tapirus terrestris (Perissodactyla, Tapiridae)

In Brazil, there are two species of tapirs, the largest land mammals in Brazil, which belong to the order Perissodactyla, as do horses. Our aim was to describe the bone and muscular anatomy of the forearm and hand in T. terrestris and to propose adaptive functions. We used ive anatomical specimens donated from a breeder to the Laboratory for Teaching and Research on Wild Animals of the Federal University of Uberlandia after death with no trauma. The bones were analyzed, the muscles dissected, and both described. The bones of the forearm and hand of the tapir are the ulna, radius, Os. metacarpalia, Os. carpi, phalanx and Os. sesamoideum.

The tapirs are ungulate animals, which are characterized by having an odd number of ingers, and they stand on the ends of their ingers (EISENBERG; REDEFORD, 1999).Tapirus terrestris, in contrast, has four ingers on the hand and three ingers on the foot.
These animals have a wide geographical distribution in South America, and speciically in Brazil, it is distributed in all biomes, except in the extreme south of the Pampas (PADILLA; DOWLER, 1994;BROOKS et al., 1997).It is extinct in the Caatinga (MEDICI et al., 2012) and its relative density is considered low in the state of Paraná (VIDOLINI et al., 2011).
The anatomy and physiology of the tapir are similar to that of the domestic horse and other Perissodactyla (HERNÁNDEZ-DIVERS, et al., 2007;RINCÓN, 2008).Tapirus terrestris is of great importance in the environment as a seed disperser, and it has tight integration in food webs (VIDOLINI et al., 2011).However, this species is exposed to different threats (MEDICI et al., 2012).
According to Heleno et al. (2011) and Rosa et al. (2012), the morphological description of wild species helps in interventions at the surgical and clinical-surgical levels and in conservation policies, and also helps the enhancement of applications in the veterinary and therapy clinic.
Tapirus terrestris has a wide distribution and importance for the environment, and it is considered a species vulnerable to extinction.Therefore, besides evaluating the importance of information on the anatomy of wild animals, we aimed to describe the bone and muscle anatomy of the forearm and hand of T. terrestris and to propose adaptive functions.

Material and Methods
We used five anatomical specimens of adult animals donated by a breeder to LAPAS-UFU after natural death without trauma.The specimens were ixed in aqueous 10% formalin in opaque vats.The study was approved by the Ethics Committee for Use of Animals of the UFU (CEUA) under n o 069/12, and was in accordance with Normative Ruling n o 03, September 1, 2014 of ICMbio.
For the description of bones, four anatomical specimens were macerated in boiling water and subsequently placed in hydrogen peroxide solution for 12 h for bleaching.For the muscle study, two of the ive anatomical specimens were carefully dissected, according to the usual techniques in gross anatomy, preserving the attachment points and features of the muscles.The nomenclature adopted was according to the International Committee on Veterinary Gross Anatomical Nomenclature (2012).
For the complementation of the description, radiological images were taken to check the position of the bones after the maceration process and to help in the assembly of the skeleton.The images were recorded with a digital camera (Nikon Coolpix L820 16 Mpx Zoom 30x) and by the radiographic imaging apparatus of the Veterinary Hospital of UFU (Siemens RZ9), and the photographs were handled using Adobe Photoshop software CC 14.
Bone and muscular anatomy of the forearm and hand in T. terrestris

Results and Discussion
The bones that constitute the forearm skeleton of T. terrestris are the ulna and radius, since the bones of the hand, os.metacarpalia, os.carpi, phalanx and os.sesamoideum.The ulna of T. terrestris articulates proximally with the humerus and its into the fossa olecrani, and it is fused to the radius, like in Ozotoceros bezoarticus (pampas deer) (VARELA, 2010).Differently from horses, the radius and ulna have their distal part at the same height for the articulation with the carpi.They are long bones, which help in moving over long distances and supporting the body weight upright (BARBIERI et al., 2011).
The radius (Figure 1) is a long bone and it is located cranially to the ulna, the articular carpal surface, the distal part of the radius, is smooth, and it articulates with the carpal bones, all these features are quite similar to those described by Dyce et al. (2010) for cattle.The carpal bones in T. terrestris (Figures 2 and 3) are a set of seven short bones divided into two rows, proximal and distal, the same as in cattle and horses (DYCE et al., 2010).(2000), the morphological interactions of cursorial legs with the environment reinforce the notion that there may be a mutualistic maintenance to maintain ecological patterns and processes between the disperser and seeds, especially in megalora, due to the habit of T. terrestris covering large areas.
Tapirus terrestris has the phalanges articulating with the metacarpal bones in the metacarpal sequence II, III, IV and V (Figures 4 and 5).There are eight sesamoid bones, two for each phalanx, and they have articular function and help change the direction of the tendons or increase lever strength for the muscles and tendons of the hand (GETTY et al., 1986).According to Hildebrand (1995), the longer the leg, the longer the step is, and the forelegs of T. terrestris are elongated, and its four ingers also help in its moving (CAMPBELL, 1936).
Tapirus terrestris has bone and muscle characteristics of an animal adapted to moving or running and any eventual swimming with protuberant bones (PEREIRA et al., 2015).The forearm and hand muscles are divided into two groups, the extensors and lexors (Figures 6 and 7).
The M. extensor carpi radialis (Figures 6 and 7) is the largest muscle of the extensor group in T. terrestris.The M. ulnar lateralis (M.extensor carpi ulnaris) (Figure 7 and 8) in T. terrestris it is elongated.The M. lexor carpi radialis is a muscle that is located on the medial side of the forearm.The M. lexor carpi ulnaris (Figure 6) is long and slender.The M. extensor digitorum communis located laterally to the M. extensor carpi radialis (Figure 7 and 8) the same as in ruminants according to König and Liebich (2002).The M. extensor longus of the II, III, IV and V is attached to this muscle, the same as in horses, cattle and pigs (KÖNIG;LIEBICH, 2002).The M. extensor digitorum lateralis (Figure 7) is located caudally to the M. extensor digitorum communis and cranially to M. ulnar lateralis.The M. abductor longus of the digiti, is located at the lateral portion of the radius, it is an elongated muscle.The M. lexor digitorum supericialis in T. terrestris (Figure 7) is divided into two parts (shallow and deep), and it is situated in the forearm.This muscle has two tendons in the palmar aspect of the carpus.The M. lexor digitorum profundus in T. terrestris (Figure 6) is divided into three parts; radial, humeral and ulnar.The M. extensor carpi oblique located on the cranial surface (Figure 7) is a small muscle that is obliquely connected to the radius.The Mm. interossei of T. terrestris are mostly composed of ibrous tissue (Figure 9).They are situated on the palmar side, between the metacarpal bones II, III, IV and V, and they are made up of supericial and deep parts.The Mm. lumbricales are divided into lateral and medial and are little evident (Figure 9).The protuberant muscles reinforce their function in strength and resistance for running and eventual swimming (HILDEBRAND, 1995).Table 1 presents the origin, insertion and inference of action of the described muscles.On the basis of the results, we conclude that the bones of the forearm and hand of T. terrestris have specific characteristics that give this mammal the capacity of moving over long distances and weight bearing.As mentioned above, even with an even number of ingers (four) on the hand, it is assigned to the order Perissodactyla, and it is believed that inger V helps in moving and the resting position.They have the same number and arrangement as in horses, also showing similarities with other wild animals.Tapirus terrestris has bone and muscle characteristics suitable for moving at a fast pace and eventual swimming with obvious bone features and protuberant muscles.

TABLE 1 :
Origin, insertion and inference of action of the forearm and hand muscles of Tapirus terrestris.Bone and muscular anatomy of the forearm and hand in T. terrestris