Borhyaenidae

Abstract: Marshall, L. G. (Department of Geology, Field Museum of Natural History, Chicago, Illinois 60605) 1977. Cladistic analysis of borhyaenoid, dasyuroid, didelphoid, and thylacinid (Marsupialia: Mammalia) affinity. Syst. Zool. 26: 410-425.-A cladistic analysis of the marsupial order Marsupicarnivora is made in an attempt to clarify borhyaenid-thylacinid affinity. This analysis is made in consideration of importance of weights for homologous character states as recognized by Hecht (1976), and Hecht and Edwards (1976). Apomorphies in borhyaenids which separate them from thylacinids include presence of a nasal-lacrimal contact, a solid palate, and reduction or loss of the transverse canal. Apomorphies in thylacinids which separate them from borhyaenids include reduction in size of dP4 and presence of an epitympanic squamosal sinus. The "dog-like" marsupials of Australia (thylacinids) and South America (borhyaenids) appear to represent a classic example of parallelism in evolution; thylacinids having evolved from a common ancestor shared with Australian dasyuroids, and borhyaenoids having evolved from a common ancestor shared with didelphoids. Reduction or loss of the metaconid and stylar shelf, loss of ossified epipubic bones, and reduction of incisors to 4/3 apparently occurred independently and in parallel in borhyaenids and thylacinids. [Borhyaenidae; Thylacinus; Marsupicarnivora; cladism.] It is reasonably well established that Australia and South America were island continents during most of the Tertiary Period (ca. 65 through 2 my BP; Tedford, 1974). For South America this isolation ended a few million years ago when the Panamanian Land Bridge came into existence uniting the two Americas. Thereafter, the fossil record documents an intermingling of the respective faunas. Australia, on the other hand, has retained its geographic isolation. A feature of this isolation is that marsupials came to fill the roles of large mammalian predators in both Australia and South America, niches occupied on other continents by placental carnivores. In South America the "dog-like" marsupials belonged to the family Borhyaenidae, a fossil group known from beds of late Paleocene (Riochican) through late Pliocene (Montehermosan) age. The Australian "dog-like" marsupials are represented by a single genus, Thylacinus, family Thylacinidae, with a known range extending from Miocene (Cheltenhamian) through Recent. Thylacinus became extinct on the Australian mainland about 3,200 yr BP, was still present in New Guinea by about 10,000 yr BP (Archer, 1974a; Van Deusen, 1963), and survived in Tasmania until the early part of this century (Archer, 1974a). A major issue confronting mammalian taxonomists and biogeographers is the phylogenetic affinity of the Australian and South American "dog-like" marsupials. The issue boils down to two basic points of view: 1) borhyaenids and thylacinids share a common ancestor not shared with other marsupials (they are a monophyletic group); or 2) the similarities in these groups are due to parallelism in evolution, with thylacinids having evolved from a common ancestor shared with Australian dasyuroids, and borhyaenids having evolved from a common ancestor shared with didelphoids. The purpose of this paper is to apply cladistic analysis to the Australian and South American marsupial order Marsupicarnivora (sensu Ride, 1964) in an attempt to clarify borhyaenid-thylacinid affinity. The theory of cladism, a logical framework for determining phylogeny,

Abstract: Two new species of fossil Marsupialia are described from beds of late Tertiary age on the Altiplano south of La Paz, Bolivia. Borhyaenidium altiplanicus n. sp. (Borhyaenidae, Hathlyacyninae) is erected on a specimen from the Mauri VI "Formation" of Huayquerian (late Miocene) age near Achiri. B. altiplanicus is the most generalized of known species of Borhyaenidium and differs little from its probably Santacrucian (early Miocene) ancestor Perathereutes pungens Ameghino, 1891. Borhyaenidium was previously known only from beds of Huayquerian and Montehermosan (Pliocene) age in Argentina. Sparassocynus heterotopicus n. sp. (Didelphidae, Sparassocyninae) is based on a specimen from the Umala Formation of Montehermosan age near Umala. S. heterotopicus is the most generalized species of Sparassocynus known, and is the first species known outside of Argentina, where the genus is recorded from beds of Huayquerian through Uquian (early Pleistocene) age.--Journal abstract.

Abstract: An almost complete mandible of Patene simpsoni (Marsuplalia, Borhyaenidae, Hathlyacyninae) from Lumbrera Fm. (Casamayoran Age, early Eocene) of Salta Province, Argentina, is described. By means of a sedimentary analysis of this formation, there can be distinguished five facies: St, Sp, Sr, Sh and FI-Fm. From a palaeoenvironmental point of view, this formation appears related to a meander system, with the Iluctuant variations that characterize ephemeral interlaced rivers. The sedimentary sequence reflects alternative conditions, probably corresponding to humid and dry epochs. The material examined represents the first record of a mandible of Patene simpsoni, and extends its known range from Itaboraian Age (middle Paleocene) to Casamayoran Age (Eearly Eocene). P. simpsoni shares some morphological features with several Didelphoidea from the South American Paleogene, specially with those from tbe Paleocene of Itaborai, Brasil (e.g., p3 notably enlarged in relation to p2.). Nevertheless, it already shows those features that define a more intense carnassialization, typical of the Borhyaenidae (e.g., reduced metaconid and smaller than paraconid ). This association of specialized fea tu res is interpreted as prernonitory to the more advanced Borhyaenoidea, and as distinguishing it from the known Didelphoidea. Climatic-environmental differences between the North of Argentina and Patagonia during early Eocene could explain the morphological difference Found among the two known species of Patene, P. simpsoni and P. coluapiensis. In turn, the presence of P. simpsoni up to early Eocene, at least, in the present intertropical regions seems to indicate the ertdurance there of the environmental conditions that characterized the Paleocene high latitudes.