Systematics

I specialize in notoungulate systematics but have published studies on a variety of other South American mammals. Representative publications on various groups are summarized below with links to their full citations.

Holotype cranium of the mesothere Eutypotherium superans, side view, nose to right.

Holotype cranium of the mesothere Eutypotherium superans, side view, front to right. Photo by D. Croft. Reuse permitted under CC BY-NC-SA 2.0.

Notoungulates: Much of my research has focused typothere notoungulates, which include interatheres, archaeohyracids, mesotheres, and hegetotheres. Many of these papers have described new species (e.g., Croft 2007 names a new interathere, Croft et al. 2016 names a new hegetothere) and/or included a phylogenetic analysis of the group (e.g., Croft et al. 2003 for archaeohyracids; Croft et al. 2004 for mesotheres; Croft and Anaya 2006 for hegetotheres; Shockey et al. 2012 for leontiniids). In other papers, my colleagues and I have reported new occurrences of previously known species (e.g., Croft et al. 2003 for the toxodontid Nesodon conspurcatus), described the species at a particular site (e.g., Croft et al. 2004 for Chucal, Chile; Croft 2007 for Quebrada Honda, Bolivia; Croft et al. 2009 and Croft et al. 2016 for Cerdas, Bolivia) or analyzed variation within a particular sample (Townsend and Croft 2010 for early Miocene mesotheres from Bolivia). I have also been involved with studies of notoungulate ear regions using computed tomography (CT) scanning in order to discover features that may shed light on their evolutionary relationships (see Macrini et al. 2010 and 2013).

Litopterna

Cranium of the macraucheniid Promacrauchenia sp., side view, front to right. Photo by D. Croft. Reuse permitted under CC BY-NC-SA 2.0.

Litopterns: I have not yet published any papers exclusively devoted to litopterns, but I have described remains of macraucheniids (robust litopterns) from Chucal, Chile (Croft et al. 2004) and Cerdas, Bolivia (Croft et al. 2009). We have collected some very nice specimens of both macraucheniids and proterotheriids (gracile litopterns) from Quebrada Honda, Bolivia, and I am in the process of describing these remains along with students from CWRU.

Xenarthrans

Holotype left lower jaw of the glyptodont Parapropalaehoplophorus septentrionalis, side view, front to left. Photo by D. Croft. Reuse permitted under CC BY-NC-SA 2.0.

Xenarthrans: Among xenarthrans, I have mostly worked on cingulates (armadillos, glyptodonts, and relatives). My first paper dealing with this group named a new species of glyptodont from Chucal, Chile (Croft et al. 2007). It is among the geologically oldest glyptodonts known from remains of the shell, skull, and skeleton, and we are in the process of describing the ankle bones of this species. The same paper (Croft et al. 2007) also discussed the armadillos from Chucal, which are only known from rather fragmentary remains. Similarly poor remains are addressed in our earlier summary of the fauna of Cerdas, Bolivia, along with an interesting partial lower jaw of the sloth Xyophorus (Croft et al. 2009). This specimen is noteworthy in being the geologically oldest representative of its family, Nothrotheriidae. We have collected a variety outstanding armadillo, glyptodont, and sloth remains from Quebrada Honda, Bolivia and are working to clean and describe this material.

Rodents

Cranium of the dinomyid Scleromys schurmanni, palatal (underside) view, front to right. Photo by D. Croft. Reuse permitted under CC BY-NC-SA 2.0.

Rodents: My first foray into rodent systematics was a paper on the rodents of Quebrada Honda, Bolivia that named two new species (Croft et al. 2011). Since then, I have collaborated on a paper describing the oldest rodents in South America, which come from eastern Peru (Antoine et al. 2012). The same year, other colleagues and I published a paper on the rodents of Tinguiririca, Chile, which were formerly the oldest rodents on the continent (Bertrand et al. 2012). I am now working on a new species of chinchillid from Chucal, Chile, which was mentioned in the initial paper we published on that fauna (Flynn et al. 2002). We have found another, closely-related species at two sites in Bolivia and will discuss that in the same paper. I am also involved with projects on identifying the species of Prolagostomus (a type of chinchillid) and Acarechimys (a very small octodontoid) at Quebrada Honda.

Sparassodonts

Holotype cranium of the borhyaenid Acrocyon riggsi (partially reconstructed), side view, front to right. Photo by D. Croft. Reuse permitted under CC BY-NC-SA 2.0.

Marsupials: Sparassodonts (South American meat-eating marsupials (sparassodonts) tend to be quite rare in the fossil record, but we have managed to find a few specimens in Chile and Bolivia. The specimens from Chile are under study, but a student of mine and I have published two papers on sparassodonts from Bolivia. One of these described a new (but unnamed) species from Quebrada Honda and analyzed the evolutionary relationships of the group (Engelman and Croft 2014). The other discussed new material of Acyon myctoderos from the same site (Engelman et al. 2015). Another group of marsupials we have been working on are paucituberculatans, relatives of modern shrew-opossums (caenolestids). One paper we published suggested that two species of the genus Acdestis from southern Argentina actually represent males and females of a single species (Engelman and Croft 2016). The early version of another paper that names several new species of palaeothentids from Quebrada Honda, Bolivia was published recently (Engelman et al. 2016).

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