page_title: Transandinomys bolivaris
section_title: Skull and teeth
hierarchical_section_title: Transandinomys bolivaris / Description / Skull and teeth
caption_attribution_description: English: Mandible of Oryzomys bombycinus bombycinus (now Transandinomys bolivaris), seen from the left. This is specimen USNM 171103, an adult female from Cerro Azul, Panama.
context_page_description: Transandinomys bolivaris, also known as the long-whiskered rice rat, is a rodent in the genus Transandinomys. It is found in humid forest from northeastern Honduras to western Ecuador, up to 1,800 m above sea level. Since it was first described in 1901 from Ecuador, six scientific names have been introduced for it, but their common identity was not documented until 1998 and the species has long been known under the name Oryzomys bombycinus, described from Panama in 1912. The name Oryzomys bolivaris was used before it was moved to the new genus Transandinomys with Transandinomys talamancae in 2006.
  It is a medium-sized rice rat distinguished by its very long vibrissae —those above the eyes are up to 50 mm long. The fur, which is soft and dense, is usually dark brown above and light gray below; it is darker in juveniles. The feet are long and the tail is about as long as the head and body. The skull is narrow and has a broad interorbital region. The species generally lives on the ground. Although it is rare, its conservation status is thought to be secure.
context_section_description: The skull is relatively long and has a long, narrow rostrum (front region), broad interorbital region (between the eyes) and narrow braincase with almost vertically oriented walls at the sides and behind. It differs from that of T. talamancae in various proportions. Although the subspecies previously recognized in "Oryzomys bombycinus" have been separated by small differences in skull features, Pine rejected these on the basis of his much larger samples. Musser and colleagues agreed, but noted that Colombian animals appeared to have larger skulls. The zygomatic plates are broad and the zygomatic arches (cheekbones) behind them are nearly parallel to each other. The margins of the interorbital region contain prominent beads, which extend to the braincase as temporal ridges; these are usually less well-developed in T. talamancae. Unlike in T. talamancae and H. alfaroi, the parietal bone is usually limited to the roof of the braincase and does not extend to the sides.
  The incisive foramina, which perforate the front part of the palate, do not extend between the molars. The palate ends beyond the third molars and is perforated by posterolateral palatal pits there. Behind it, the roof of the mesopterygoid fossa is perforated by poorly developed sphenopalatine vacuities. The auditory bullae, which house the inner ear, are large. Usually, the mastoid bone lacks openings (fenestrae), which are present in T. talamancae. The pattern of the arteries in the head is primitive, as indicated by the condition of various foramina (openings) and grooves in the skull.
  The mandible (lower jaw) looks chunky and has a long condyloid process at its back; that of T. talamancae is more slender. The capsular process, a projection at the back of the jaw which houses the root of the lower incisor, is poorly developed.
  The incisors are large and ungrooved. Their enamel is orange, but paler on the lowers. The orientation of the upper incisors is opisthodont, with the cutting edge oriented backwards. The molars are brachydont (low-crowned) and have two rows of main cusps separated by deep valleys and complemented by a network of crests and smaller cusps. The first upper molar is broader than in T. talamancae. As in this species, but unlike in many other rice rats, including H. alfaroi, the mesoflexus on the second upper molar, which separates the paracone (one of the main cusps) from the mesoloph (an accessory crest), is not divided in two by an enamel bridge. The hypoflexid on the second lower molar, the main valley between the cusps, is very long, extending more than halfway across the tooth; in this trait, it is similar to T. talamancae but unlike H. alfaroi. Each of the upper molars has three roots (two on the outer and one on the inner side) and each of the lowers has two (one at the front and another at the back).
caption: Mandible (lower jaw) of Transandinomys bolivaris from Cerro Azul, Panama[60]
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