Pedal Digit Research Articles

Dinosaurian precursors from the Middle Triassic of Argentina:Lagerpeton chanarensis

ABSTRACT We describe the holotype and referred material of the unusual Middle Triassic dinosaur precursor, Lagerpeton chanarensis. The autapomorphies of Lagerpeton chanarensis include the convex and fluted puboischial flange, hook-shaped femoral head, elongate femoral fourth trochanter, fused astragalocalcaneum, tall posterior ascending process on the astragalus, and functionally didactyl pes. Among ornithodirans, Lagerpeton chanarensis is more closely related to dinosaurs than are pterosaurs. We list tarsal and pedal synapomorphies shared by Lagerpeton chanarensis and other dinosauromorphs that are absent in pterosaurs and crurotarsal archosaurs. These include an increase in the relative size of the central metatarsals and subparallel orientation of pedal digit V. There is no evidence that Lagerpeton and other small-bodied dinosauromorphs in the Los Chañares fauna, namely “Lagosuchus” lilloensis, comprise a monophyletic group. The digitigrade pes and the elongate and erect hind-limbs of basal pterosaurs and dinosauromorphs suggest that an obligatory bipedal posture had evolved in early ornithodirans. In extant vertebrates, obligatory bipedal posture is often associated with either cursorial or saltatory locomotor habits. Although these two locomotor patterns are difficult to distinguish on skeletal traits alone, the anteriorly inclined dorsal neural spines, small pelvic girdle, fused proximal tarsals, and very narrow didactyl pes in Lagerpeton chanarensis suggest that it may have been a saltator.

Open quiz solution: Case report 784

In summary, we have reported on an unusual form of fibrous dysplasia, presumptively monostotic, localized to the middle phalanx of the second pedal digit, and presenting as a mass. Monostotic fibrous dysplasia of phalanges of the foot is rare, but should be considered in the differential diagnosis of a mass in the foot.

Vertical clinging, small body size, and the evolution of feeding adaptations in the Callitrichinae.

Primates of the subfamily Callitrichinae (Callimico, Callithrix, Leontopithecus, and Saguinus) are small-bodied New World monkeys (105-700 g) possessing clawlike nails on all manual and pedal digits excluding the hallux. Specialized nails in these genera serve a critical function in feeding by enabling tamarins and marmosets to cling to trunks and other large vertical supports while exploiting food resources. Within the subfamily, there is evidence of at least four distinct large-branch feeding patterns. These include (1) seasonal exudate feeding and occasional trunk foraging (many Saguinus spp.); (2) exploitation of bark surface insects and the use of trunks as a platform to locate terrestrial prey (Saguinus fuscicollis, S. nigricollis, and Callimico); (3) manipulative foraging and bark stripping to locate concealed insects and small vertebrates (Leontopithecus); and (4) tree gouging and year-round exudate feeding (many Callithrix). Large-branch feeding and the use of vertical clinging postures appear to be a primary adaptation among virtually all callitrichines, distinguishing them ecologically from other platyrrhine taxa. Given the anatomy and behavior of extant callitrichines, Saguinus appears to be the most ecologically generalized member of this subfamily, and species of this genus may provide useful models for reconstructing the feeding and foraging adaptations of early callitrichines.

Tarsiers, adapids and the integrity of Strepsirhini

Although strepsirhine primates can be described by their narial configuration, this and most other definable features are probably primitive retentions; only the development of a grooming claw of the second pedal digit and of a toothcomb (the latter of which has been lost in Daubentonia) emerge as potential apomorphies of the group. Within this assemblage lemurids, Lepilemur, the indriids, and Daubentonia can be argued to constitute a monophyletic group whose relationships cladistically are in the sequence listed; Lemuridae and Indriidae can themselves be delineated as monophyletic groups. The remaining strepsirhine primates—the cheirogaleids, galagids, and lorisids—also appear to constitute a definable clade, with the former group representing the sister taxon of the latter two families; cach family can be united on the basis of distinct synapomorphies. Although there are features—especially of the ear region—which present themselves as potentially reflective of the sister relationship of Tarsius + Anthropoidea, other characters, including the possession of the grooming claw, are suggestive of an alternative scheme: Tarsius may be the sister of the extant lorisiform group, thereby reconstituting, albeit in a novel form, the primate suborder Prosimii. It also appears that fossil “tarsioids” may in fact be more closely related to the extant lorisiforms than to Tarsius. A reconsideration of the so-called fossil lemurs, the adapids, leads to the conclusion that Adapis-like primates are a clade apart from Pelycodus, Notharctus, Smilodectes and their most immediate relatives, and may themselves constitute a clade that is related as the primitive sister to all other “prosimians” by virtue of the development of the so-called free intrabullar tympanic ring.

Ainhum (dactylosis spontanea); report of a case.

Ainhum is from a verb in the Yoruba language meaning saw or file. 42 The term was first applied to an unusual chronic disease affecting the pedal digits, 14 and sometimes the fingers,11 by the African Negroes. The condition was reported by Clarke in 1860. 16 He described it as dry gangrene. It was not until da Silva Lima became aware of the disease in Brazil and reported on it in the Medical Gazette of Bahia 17 that the definitive entity was described and the name ainhum formally accepted. A pathologic study by Wucherer in 1872 54 marked the next phase in the elaboration of the entity. Facio, in 1924, contributed a roentgenologic demonstration to the description of the disease. 22 Dactylosis spontanea occurs principally among the colored races, particularly Negroes, and mainly in men between the ages of 25 and 45. 14 Cases have been reported in