Callistoe vincei, a new Proborhyaenidae (Borhyaenoidea, Metatheria, Mammalia) from the Early Eocene of Argentina

A new species of small-bodied sparassodont (Mammalia, Metatheria) from the middle Miocene locality of Quebrada Honda, Bolivia

“…However, unlike some studies, we did not recover a monophyletic clade of Proborhyaenidae + Thylacosmilidae (Babot et al, 2002), nor a paraphyletic Proborhyaenidae (Babot, 2005, in Argot andBabot, 2011). Rather, in contrast to , we recovered thylacosmilids as the sister group to borhyaenids.…”

“…The canine alveoli of UF 27881 are also relatively large for a non-borhyaenoid sparassodont, second only to a specimen of Cladosictis patagonica (MACN A 5927). Aside from MACN A 5927 and a specimen of Acrocyon riggsi (FMNH P13433), all sparassodonts with proportionally larger canines than UF 27881 (i.e., proborhyaenids and Arctodictis) are species that have been noted to possess abnormally large canines relative to the rest of the group (Marshall, 1978;Babot et al, 2002).…”

“…In contrast to eutherians, sparassodont canines are either open-rooted (e.g., proborhyaenids and thylacosmilids; Babot et al, 2002) or form roots late in life (e.g., hathliacynids and borhyaenids; Marshall, 1976c). Riviere and Wheeler (2005) suggested that the presence of enlarged gum tissue in Smilodon represents an adaptation towards greater precision when biting, which would be essential for a mammal with hypertrophied canines that would be vulnerable to torsion forces created by struggling prey (Akersten, 1985;Van Valkenburgh and Ruff, 1987;Salesa et al, 2005).…”

“…Although there has been some discussion of the size of the largest sparassodonts (Babot et al, 2002;Ercoli and Prevosti, 2011), few studies have investigated the lower size limit of this group (Marshall, 1981;Ercoli and Prevosti, 2011;Prevosti et al, 2012). In his review of the then-known species of small-bodied sparassodonts, Marshall (1981) considered the late early Miocene (Santacrucian) hathliacynid Pseudonotictis pusillus to be the smallest known member of this group.…”

“…(Marshall, 1978) from the fissure-fill deposits at Itaboraí, Brazil, which may be late Paleocene or early Eocene in age (Gelfo et al, 2009). Following this early Cenozoic origin, sparassodonts diversified into a wide variety of forms by the latter half of the Eocene, including the robust 'bear-like' or 'wolverine-like' proborhyaenids Callistoe and Arminiheringia (Babot et al, 2002;Argot and Babot, 2011). The nested position of proborhyaenids within the Sparassodonta suggests that most of the major groups of sparassodonts had originated by this time (Babot et al, 2002;Forasiepi, 2009:fig.…”