ISOLATED PETROSAL OF THE EXTINCT SLOTH GLOSSOTHERIUM TROPICORUM (XENARTHRA, FOLIVORA, MYLODONTIDAE) FROM THE ISLAND OF TRINIDAD Timothy J. Gaudin and Joseph Broome Vol. 58, No. 3, pp. 51–64 September 2, 2021 ISSN 2373-9991 UNIVERSITY OF FLORIDA GAINESVILLE BULLETIN of the Florida Museum of Natural History The FLORIDA MUSEUM OF NATURAL HISTORY is Florida’s state museum of natural history, dedicated to understanding, preserving, and interpreting biological diversity and cultural heritage. The BULLETIN OF THE FLORIDA MUSEUM OF NATURAL HISTORY is an on-line, open-ac- cess, peer-reviewed journal that publishes results of original research in zoology, botany, paleontology, archaeology, and museum science. New issues of the Bulletin are published at irregular intervals, and volumes are not necessarily completed in any one year. Volumes contain between 150 and 300 pages, sometimes more. 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Publication Date: September 2, 2021 This and other recent issues of the Bulletin can be freely downloaded at: https://www.floridamuseum.ufl.edu/bulletin/publications/ Send communications about this publication to: Bulletin Committee; Florida Museum of Natural History; University of Florida; P.O. Box 117800; Gainesville, FL 32611-7800 USA FAX: 352-846-0287; Email: bulletin@flmnh.ufl.edu URL: https://www.floridamuseum.ufl.edu/bulletin/home/ Cover image: Lateral view of an isolated left petrosal (UF 240205) of Glossotherium tropicorum from Pleistocene tar pits of Trinidad. http://zoobank.org/ ISOLATED PETROSAL OF THE EXTINCT SLOTH GLOSSOTHERIUM TROPICORUM (XENARTHRA, FOLIVORA, MYLODONTIDAE) FROM THE ISLAND OF TRINIDAD Timothy J. Gaudin1 and Joseph Broome1 1University of Tennessee at Chattanooga, Department of Biology, Geology & Environmental Science, 615 McCallie Avenue – Dept 2653, Chattanooga, TN 37403-2598, USA < Timothy-Gaudin@utc.edu> Gaudin, T. J. and Joseph Broome. 2021. Isolated petrosal of the extinct sloth Glossotherium tropicorum (Xenarthra, Folivora, Mylodontidae) from the island of Trinidad. Bulletin of the Florida Museum of Natural History 58(3):51–64. ABSTRACT This report is the first to identify the presence of the extinct ground sloth Glossotherium tropicorum from Pleistocene-aged tar pit deposits in Trinidad. G. tropicorum is known primarily from extensive skeletal material recovered from the Pleistocene of western Ecuador and Peru. Our identification is based on an isolated left petrosal bone, which exhibits a variety of derived diagnostic features of mylodontid sloths in general, e.g., the presence of an epitympanic recess, and the genus Glossotherium in particular, including a reduced anteroventral process of the tegmen tympani. This represents only the second published record of the genus Glossotherium from outside continental South America, and is a substantial range extension for the species G. tropicorum. The present study also represents the first published description of a mylodontid sloth fossil from Trinidad. The specimen is part of a collection that was initially documented in an unpublished Master’s thesis, and that includes additional sloths and other Pleistocene mammals. This fauna confirms the presence of extensive savanna-type habitats on Trinidad during the Pleistocene, and is consistent with the presence of a land bridge connection between the island and mainland South America at that time. KEY WORDS: Sloths, Glossotherium, Trinidad, Pleistocene, tar pit, ear region, skull, anatomy TABLE OF CONTENTS Introduction .............................................................................................................51 Materials and Methods ............................................................................................53 Description ..............................................................................................................55 Discussion ...............................................................................................................59 Conclusion ..............................................................................................................61 Acknowledgments ..................................................................................................61 Literature Cited .......................................................................................................61 52 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 58(3) INTRODUCTION Sloths are herbivorous members of the Xenarthra. Living sloths comprise a small clade of two gen- era and six species placed in two different families confined to the rainforests of South and Central America and a Caribbean island (Anderson and Handley, 2002; Gaudin, 2004; Varela et al., 2018; Preslee et al., 2019; Delsuc et al., 2019). They rep- resent only a small remnant of a much more diverse radiation that was found throughout the Americas, from Alaska to Patagonia, including some of the is- lands of the Caribbean, and numbering at least 100 genera (e.g., McKenna and Bell, 1997; McDonald and De Iuliis, 2008; Pujos et al., 2012). The major- ity of these extinct sloths were terrestrial, and had a body size much greater than that of living sloths, some at least as large as modern-day elephants, and likely displayed more dietary diversity than living forms (e.g., McDonald and De Iuliis, 2008; Bargo and Vizcaíno, 2009; Pujos et al., 2012; Resar et al., 2013; Dantas et al., 2017). However, all large terrestrial sloths became extinct in the megafau- nal extinction event at the end of the Pleistocene (McDonald and De Iuliis, 2008), except for some Antillean taxa (Steadman et al., 2005). Our knowl- edge of this great sloth radiation has increased rapidly over the past few decades, and numerous new taxa have been recognized (e.g., McDonald and De Iuliis, 2008; Pujos et al., 2012; Varela et al., 2018; Boscaini et al., 2019). One such recently recognized taxon is a mylodontine sloth Glossoth- erium tropicorum, which is known from localities in northwestern South America, including parts of southwestern Ecuador and the northernmost por- tions of Peru (Fig. 1; De Iuliis et al., 2017). The subject of the present report is a single fossil specimen housed in the collections of the Florida Museum of Natural History, recovered from tar pit deposits on the present-day island of Trinidad, which is situated just off the Venezuelan coast of northern South America (Fig. 1). The fos- sil is an isolated petrosal bone from a mylodontine sloth, and it is our contention that this specimen likely pertains to Glossotherium tropicorum. Although Trinidad is an island today, it lies on the coastal shelf of South America as the closest member of the Antillean chain to mainland South America. Given the repeated glaciation events dur- ing the Pleistocene epoch (2.6 Ma to 11.7Ka), and the concomitant sea level changes (Kurtén and An- derson, 1980; Pielou, 1981; Ogg et al., 2016), it is likely that Trinidad was connected repeatedly to South America over the course of its recent geo- logical history (Comeau, 1991; Mychajliw et al., 2020). Moreover, Pleistocene climate oscillations changed not only the physiographic features of the landscape, but also the structure of ecological com- munities. Areas that today are largely forested were at various points in the past covered by savannah type environments (Comeau, 1991; Webb, 1991), and this likely includes Trinidad (Wing, 1962; Co- meau, 1991; Mychajliw et al., 2020). Given this, perhaps it would not be surprising to find a large, terrestrial, grazing sloth in the fossil record of the island, and yet, such reports are scarce. The likelihood of finding such records is enhanced by the presence of tar pits on the is- land (=asphaltic deposits or asphaltic seeps, Wing, 1962; Mychajliw et al., 2020 – Wing refers to these as “oil sand” deposits). Tar pits represent a particu- larly valuable source of information on the paleo- ecology of the Pleistocene (Harris, 2015). These sites often contain a large abundance and diversity of very well-reserved fossils. Tar pits are found in all parts of the world, and may closely reflect the ecosystem of their surrounding region. The sticky tar can act as a trap to ensnare passing animals (McDonald et al., 2015; Mychajliw et al., 2020) and other parts of the biota, a function that may be facilitated by water or plant debris accumulating on the surface of the tar. Fossils of Glossotherium tropicorum have been recovered from several tar pit deposits in Ecuador and Peru (Fig. 1; De Iuliis et al., 2017). The goal of the present study is to report on the identification of a fossil of Glossotherium tropicorum, a typically South American large bod- ied, terrestrial, grazing extinct sloth in a Pleisto- cene-aged tar pit deposit from Trinidad. This will GAUDIN AND BROOME.: Isolated petrosal of the extinct sloth Glossotherium tropicorum 53 enhance our understanding of the biogeography of this sloth species, as well as the Quaternary biogeo- graphic history of Trinidad and nearby portions of northern South America. MATERIALS AND METHODS The fossil mylodontine sloth specimen is an iso- lated left petrosal (UF 240205, Figs. 2–3) housed at the Florida Museum of Natural History (University of Florida, Gainesville, FL). It was part of a col- lection recovered and described by Wing (1962), though the specimen itself was not reported in Wing’s (1962) unpublished Master’s thesis. Wing’s study area was in the Texaco Forest Reserve near Fyzabad in southwestern Trinidad and dates to the late Pleistocene (Fig. 1; 34Ka, Wing, 1962; Luja- nian SALMA, Woodburne et al., 2014). This local- ity has yielded other Pleistocene mammal remains (Wing, 1962), including gomphotheriid probosci- dean teeth, a nearly complete skeleton of the ar- mored cingulate Glyptodon sp., a partial tooth and other skeletal remains assigned to the giant mega- theriine sloth “Megatherium americanum” (almost certainly pertaining instead to the species Eremoth- erium laurillardi; see Cartelle and De Iuliis, 1995), and a single tooth ascribed to the genus “Mylodon.” The latter likely pertains to Glossotherium tropico- rum as well. The Forest Reserve fauna has not been the subject of a published study, the only report be- ing Wing’s (1962) thesis. The fossils themselves are housed at the Florida Museum of Natural His- tory and the American Museum of Natural History (Wing, 1962). For comparative purposes, we examined petrosals of Glossotherium tropicorum recovered from tar pits in Ecuador and Peru (De Iuliis et al., 2017) and housed at the Royal Ontario Museum (Toronto, Canada), including a partial skull (ROM 3146), an isolated right petrosal and squamosal bone (ROM 12673, Figs. 4–5), and an isolated left petrosal (ROM 12674, Fig. 5), the latter two likely Figure 1. A. Map of northern South America, including Trinidad and the Panamanian isthmus. The black squares represent localities where specimens of Glossotherium tropicorum have been recovered (De Iuliis et al., 2017). The black polygons represent localities where specimens of G. wegneri have been recovered (De Iuliis et al., 2020). The black circle represents the location of the single site where fossils of G. phoenesis (Cartelle et al., 2019) have been found. B. Map of the island of Trinidad, depicting the location of the village of Fyzabad, and nearby, the site of the Texaco Forest Reserve, where the fossil that is the subject of the present study was recovered. 54 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 58(3) Figure 2. Isolated left petrosal (UF 240205) of Glossotherium tropicorum from Pleistocene tar pits of Trinidad. A, B, lateral view (anterior to left), photograph and line drawing. C, D, ventrolateral view (anterior toward top), photograph and line drawing. Abbreviations: acf, aperture of the cochlear fossula (containing fenestra cochleae); aptt, anteroventral process of tegmen tympani; ci, crista interfenestralis; cp, crista parotica; dgf, digastric fossa; ecfa, ectotympanic facet; enfa, entotympanic facet/roof of internal carotid artery sulcus; er, epitympanic recess; fs, facial sulcus; fv, fenestra vestibuli; me, mastoid exposure of petrosal; ptp, posttympanic process of squamosal; pp, paroccipital process of petrosal; pr, promontorium of petrosal; oaf, occipital artery foramen; shf, stylohyal fossa; sm, superficies meatus; smf, stylomastoid foramen; sq, squamosal; th, tympanohyal. GAUDIN AND BROOME.: Isolated petrosal of the extinct sloth Glossotherium tropicorum 55 from juvenile individuals based on bone texture and the presence of open sutures. We also com- pared the Trinidad fossil to published descriptions of other mylodontine petrosals (Guth, 1961; Pat- terson et al., 1992; Boscaini et al., 2018; Román- Carrión and Brambilla, 2019). AbbreviAtions: ROM, Royal Ontario Mu- seum, Toronto, Canada; SALMA, South Ameri- can Land Mammal Age; UF, Florida Museum of Natural History, University of Florida, Gainesville, USA. SYSTEMATIC PALEONTOLOGY XENARTHRA Cope, 1889 PILOSA Flower, 1883 FOLIVORA Delsuc et al., 2001 MYLODONTIDAE Gill, 1872 GLOSSOTHERIUM Owen, 1840 GLOSSOTHERIUM TROPICORUM De Iuliis et al., 2017 referred MAteriAl–Isolated right petrosal bone (UF 240205) (Figs. 2–3). locAlity–Texaco Forest Reserve near Fyzabad, southwest Trinidad (Fig. 1). Age–34 Ka (Wing, 1962; but see Mychajliw et al., 2020), Lujanian SALMA DESCRIPTION The specimen UF 240205 includes most of the pars cochlearis of the left petrosal (housing the cochlear duct and saccule) and tympanohyal, but is missing most of the posterodorsal part of the pars cana- licularis (for the utricle and semicircular canals), including the large occipital exposure of the mas- toid generally present in mylodontid sloths (Figs. Figure 3. Isolated left petrosal (UF 240205) of Glossotherium tropicorum from Pleistocene tar pits of Trinidad. A, ventral view (anterior toward top). B, Medial view (anterior to right). Abbreviations: acf, aperture of the cochlear fossula (containing fenestra cochleae); aptt, anteroventral process of tegmen tympani; cp, crista parotica; crp, crista petrosa; ecfa, ectotympanic facet; enfa, entotympanic facet/roof of internal carotid artery sulcus; er, epitympanic recess; fv, fenestra vestibuli; iam, internal auditory meatus; pr, promontorium of petrosal; saf, subarcuate fossa; shf, stylohyal fossa; smf, stylomastoid foramen; th, tympanohyal. 56 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 58(3) Figure 4. Isolated right squamosal and petrosal of juvenile Glossotherium tropicorum (ROM 12673) from Corralito, Ecuador (De Iuliis et al., 2017). A, lateral view (anterior to right). B, medial view. Abbreviations: av, aqueductus vestibuli; cp, crista parotica; crp, crista petrosa er, epitympanic recess; fs, facial sulcus; fv, fenestra vestibuli; iam, internal auditory meatus; msqs, mastoid/squamosal suture; ptp, posttympanic process of squamosal; pp, paroccipital process of petrosal; pr, promontorium of petrosal; oag, occipital artery groove; rt, foramina for rami temporales; saf, aubarcuate fossa; zp, zygomatic process of squamosal. GAUDIN AND BROOME.: Isolated petrosal of the extinct sloth Glossotherium tropicorum 57 Figure 5. Isolated right squamosal and petrosal of juvenile Glossotherium tropicorum (ROM 12673) from Corralito, Ecuador (De Iuliis et al., 2017). A, ventral view (anterior toward top). Isolated left petrosal juvenile Glossotherium tropicorum (ROM 12674) from Corralito, Ecuador (De Iuliis et al., 2017). B, ventrolateral view (anterior toward top). Abbreviations: acf, aperture of the cochlear fossula (containing fenestra cochleae); aptt, anteroventral process of tegmen tympani; ci, crista interfenestralis; coc, cochlear canaliculus; cp, crista parotica; enfa, entotympanic facet/roof of internal carotid artery sulcus; er, epitympanic recess; fs, facial sulcus; fv, fenestra vestibuli; gf, glenoid fossa; pgf, postglenoid foramen; ptp, posttympanic process of squamosal; pp, paroccipital process of petrosal; pps, postpromontorial sinus; pr, promontorium of petrosal; oag, occipital artery groove; shf, stylohyal fossa; smf, stylomastoid foramen; sqs, squamosal sinus; th, tympanohyal, zp, zygomatic process of squamosal. 2–3; Patterson et al., 1992; Boscaini et al., 2018). A small portion of the squamosal is also present, including the posttympanic process that unites with the paroccipital process of the petrosal to form the “mastoid process” of sloths (Patterson et al., 1992; Boscaini et al., 2018). It is nearly identical to the right petrosal and squamosal of Glossotherium tropicorum (ROM 12673, Figs. 4–5) in most re- spects, except for some age-related differences - the latter specimen pertaining to a juvenile (based on the texture of the bone and its open sutures, e.g., between the posttympanic process of the squamo- sal and the paroccipital process of the petrosal), whereas UF 240205 appears fully adult, though nearly identical in size to ROM 12673. In all specimens of G. tropicorum exam- 58 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 58(3) ined, including UF 240205, the pars cochlearis is dominated by an anteroposteriorly narrow, dor- soventrally elongated promontorium which is convex laterally, similar to the condition in most sloths (Patterson et al., 1992; Gaudin, 1995, 2004). In all specimens, the promontorium extends into a rounded ventral point, medial to which the ventral surface bears a strong concavity (Figs. 3, 5). This concavity either serves as the attachment surface of the missing entoympanic element, or the roof of the sulcus for the internal carotid artery, as de- scribed in G. robustum by Boscaini et al. (2018), or perhaps it serves both functions. Dorsally, the promontorium bears the two openings typical of mammalian petrosals, the fenestra vestibuli and the aperture for the cochlear fossula, which con- tains the fenestra cochleae (Wible, 2010; Boscaini et al., 2018). The former opening is ovate antero- posteriorly in UF 240205, with a nearly identical stapedial ratio (sensu Segall, 1970; =1.65) to that of ROM 12674 (=1.72), whereas the fenestra ves- tibuli of ROM 12673 is somewhat more elongated (stapedial ratio = 1.90). The cochlear fossula ap- erture of UF 240205 faces posteriorly and some- what laterally, as is the case in other mylodontine sloths (Gaudin, 1995), but curiously, lacks a me- dial groove extending toward the entotympanic. This is another feature of the Mylodontinae, and is present in G. tarijense (Gaudin, 1995), G. ro- bustum (Boscaini et al., 2018), and G. tropicorum ROM 12674, but is also missing in ROM 12673. Dorsal and lateral to the fenestra vestibuli lies the deep facial sulcus for the facial nerve (CN VII), walled laterally by a strong crista parotica in all specimens examined in the present study. The crista parotica of UF 240205 in turns forms the medial wall to a large, well-preserved depression, slightly ovate anteroposteriorly, the epitympanic recess, with a smaller depression tucked into its posteromedial corner, the fossa incudis. This ar- rangement is typical of Mylodontidae, in contrast to other sloths in which an epitympanic sinus is present. The rostral end of the crista parotica in UF 240205 appears to bear a small anteroventral process of the tegmen tympani (Figs. 2C–D, Fig. 3A), although the size and shape of the process are somewhat obscured by matrix. Although not well preserved in the other G. tropicorum specimens, a similarly small process is present in G. robus- tum (Boscaini et al., 2018), and was identified as a synapomorphy of Lestodon, Glossotherium, and Paramylodon by Gaudin (1995). At the opposite end of the crista parotica in UF 240205, the crest joins the base of a large tympanohyal element, which expands distally and extends ventrolaterally, its circular distal surface forming much of the stylohyal fossa so character- istic of sloths (Gaudin, 1995, 2004). Immediately lateral to the shaft of the tympanohyal is the stylo- mastoid foramen, situated immediately anterior to the stylohyal fossa and opening into a groove that extends ventrolaterally. The position of this aper- ture is a distinctive feature of mylodontine sloths, whereas the orientation of the groove is character- istic of Mylodontidae as a whole (Gaudin, 1995). The stylohyal fossa itself is oriented ventrolateral- ly in UF 240205, as in other mylodontids (Gaudin, 1995), and is circular in outline as preserved, as in most sloths, though it is missing the portions normally contributed by the entotympanic and ex- occipital elements. In posterior view the stylohyal fossa is V-shaped, divided by a deep longitudinal groove (Fig. 2). This unusual arrangement is also present in G. tropicorum ROM 3146. This feature does not appear to be present in G. robustum (Bos- ciani et al., 2018), G. wegneri (Román-Carrión and Brambilla, 2019) or G. phoenesis (Cartelle et al., 2019), based on the published illustrations, and may be the best indication of the taxonomic affini- ties of UF 240205. Dorsal and lateral to the stylohyal fossa in UF 240205 is a second large aperture, the ventral opening for the occipital artery (Fig. 2). This open- ing lies just medial to the paroccipital process of the petrosal, which is distinguishable by suture from the posttympanic process of the squamosal in ROM 12673 (Fig. 4A – note the two fuse to form the so-called “mastoid process” of Patterson et al. [1992] and Gaudin [1995]). Cartelle et al. (2019) note that this opening is positioned more GAUDIN AND BROOME.: Isolated petrosal of the extinct sloth Glossotherium tropicorum 59 ventrally in G. robustum than in G. tropicorum or G. phoenesis, because the occipital artery is more fully enclosed by its canal. The condition in UF 240205 resembles that of the latter two taxa, with the ventral-most portion of the occipital artery ex- posed in an open groove that connects anteriorly to the groove emerging from the stylomastoid fora- men (as in other mylodontines; see Patterson et al., 1992; Gaudin, 1995). This feature in G. wegneri is difficult to assess based on published photographs, but it may vary. The specimen photographed by Román-Carrión and Brambilla (2019, figure 8A) appears to resemble G. robustum, but at least one specimen photographed by De Iuliis et al. (2020, Appendix 2B & C) seems to exhibit a more open groove, though its morphology appears anomalous relative to the other specimens. Lastly, the medial surface of the petrosal is also available for examination in UF 240205 (Fig. 3B). It strongly resembles the morphology de- scribed and illustrated for G. robustum (Boscaini et al., 2108), as well as that observed in the two juvenile specimens of G. tropicorum (ROM 12673 and 12674; Fig. 4B). In all these specimens, there is a large aperture for the aqueductus vestibuli in the middle of the broad, shallow subarcuate fos- sa. This aperture is floored by a medially directed crest that also forms the floor of the more anteri- orly situated internal acoustic meatus. In all these Glossotherium specimens, the deep and undivided internal acoustic meatus faces not only postero- medially, as is typical for sloths, but somewhat ventrally as well, with a horizontal ventral margin to the aperture, and an arched dorsal margin. The shape of this arch is somewhat variable: V-shaped in ROM 12674, variably quadrangular or semicir- cular in G. robustum (Boscaini et al., 2018), and semicircular in both UF 240205 and ROM 12673. DISCUSSION It is clear from its morphology that the isolated petrosal and squamosal, UF 240205, recovered from tar pit deposits on the island of Trinidad, is a mylodontid sloth, and more specifically, a member of the subfamily Mylodontinae, based in particu- lar on: 1) the presence and morphology of its epi- tympanic recess; 2) the shape and orientation of its stylohyal fossa; and, 3) the position and orienta- tion of two of its foramina, the stylomastoid fora- men and fenestra cochleae. In addition, the shape of its promontorium, the morphology of the me- dial surface of the petrosal, the presence of a small anteroventral process of the tegmen tympani, and its geographic location are all strongly indicative of its provenance in the genus Glossotherium. There are currently five species recognized within this genus: G. robustum, G. tarijense, G. wegneri, G. tropicorum, and G. phoenesis (Boscaini et al., 2019; De Iuliis et al. 2020). The first two are known largely from the southern parts of South America (McAfee, 2009; Pujos et al., 2016; Boscaini et al., 2018 – though there is a record ascribed to G. ro- bustum from northern Peru in Pujos et al., 2016), and thus it seems unlikely that our petrosal per- tains to one of these two species. G. wegneri is a high elevation species know only from the An- des mountains of Ecuador (De Iuliis et al. 2020). Although present in northern South America and geographically the closest species to Trinidad (Fig. 1), its restriction to high altitudes makes it equally unlikely to have been present in northern coastal areas adjoining Trinidad. G. tropicorum is from coastal regions of northern Peru and south- ern Ecuador, whereas G. phoenesis is endemic to easternmost Brazil. Based both on biogeography, topography and on the anatomy of the canal for the occipital artery, it seems likely that UF 240205 pertains to one of these latter two species. G. tropi- corum is geographically closer than G. phoenesis, and also shares with UF 240205 an unusual mor- phology of the stylohyal fossa, both marked by a deep longitudinal groove. On this basis, we assign UF 240205 to the latter species. If this taxonomic assignment is indeed cor- rect, this new record represents an important range extension for G. tropicorum, which is currently known with certainty only from localities in north- westernmost Peru and southwestern Ecuador (De Iuliis et al., 2017), in the westernmost, coastal part 60 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 58(3) of northern South America. This results in a range extension of more than 3500 km. It is worth not- ing that De Iuliis et al. (2017) identify unconfirmed specimens assigned to G. tropicorum from Panama (Gazin, 1957; 2100 km from Trinidad) and north- ern Venezuela (Bocquentin-Villanueva, 1979; 1200 km from Trinidad). Pujos et al. (2016) also note the presence of Glossotherium sp. remains from Venezuela, which, if confirmed as G. tropicorum, might serve as a further geographic link between our specimen and the mainland records of this spe- cies. Moreover, our new record, along with the other unconfirmed records, suggest that the range of G. tropicorum may have encompassed much of northern, or at least northwestern, South America. In addition to extending the range of G. tropicorum, this specimen constitutes only the second record of the genus Glossotherium from outside continental South America (the first being Gazin’s [1957] record from Panama). As noted in Boscaini et al. (2019), the distinction between the genus Paramylodon and Glossotherium is largely a geographic one, with the former occupying North America and the latter occupying South America. It would appear, however, that the historic range of Glossotherium extended beyond modern South America, albeit not a great distance. This (and the other Trinidad Pleistocene sloth records) also rep- resents a second, much later incursion by sloths into the islands of the Caribbean, separate from the middle Cenozoic immigration event that pro- duced the endemic radiation of Antillean megal- onychid sloths (Iturralde-Vinent and MacPhee, 1999; McDonald and De Iuliis, 2008; Phillipon et al., 2020) This new record of G. tropicorum represents the first published, detailed description and illustra- tion of a mylodontid sloth fossil from the island of Trinidad, and one of very few reports of sloth fossils of any kind from the island. Wing (1962), in her Master’s thesis, previously documented the presence of fossil sloths on Trinidad, but she did not illustrate any specimens, and never published her findings. She reports the presence of the genus “Mylodon” based on an isolated molar, but giv- en the new data from the present study, it seems likely that the molar derives from Glossotherium tropicorum instead. MacPhee and Reguero (2010) published an illustration of tooth histology from a specimen of Glossotherium (AMNHVP 143455, listed as “Glossotherium sp.”, but likely G. tropico- rum) from Trinidad, but included no real descrip- tion of the specimen. Wing (1962) also reported the presence of the megatheriid sloth “Megatherium” based on a partial tooth and other isolated skeletal remains, but based on what we know of megatheri- id biogeography, these were almost certainly speci- mens of Eremotherium laurillardi (Cartelle and De Iuliis, 1995, 2006; Pujos et al., 2016). Schaub (1935) had earlier recorded the presence of this ex- tinct sloth on Trinidad, based on an isolated partial astragalus that he described but did not figure. Lastly, the presence of G. tropicorum on Trinidad in the Pleistocene provides further con- firmation of the presence of open habitats on the island at this time, as well as the existence of a sa- vannah corridor that connected South America to surrounding islands and the Central American isth- mus during the Great American Biotic Interchange (GABI; Comeau, 1991; Webb, 1991; Mychajliw et al., 2020). The change in flora from savannah to tropical evergreen and deciduous forest is docu- mented in the fossil record of Trinidad, as reflected particularly in midden deposits recovered from the island (Wing, 1962; Comeau, 1991). The record also confirms that the plant life of Trinidad oscil- lated between the tropical forest typical of mod- ern Trinidad during interglacial periods, and drier deciduous forest and savannah during colder and more arid periods corresponding to glacial inter- vals (Wing, 1962; Comeau, 1991; Mychajliw et al., 2020). This is reflected in the faunal remains, as indicated by the presence of other savannah- dwelling Pleistocene mammal species, including gomphotheres and glyptodonts (Blair, 1927; Wing, 1962; Sánchez-Chillón et al., 2003; Vizcaíno et al., 2011; Mychajliw et al., 2020). Unsurprisingly, the Trinidad flora and fauna resemble South American plant and animals during the Pleistocene (Blair 1927; Wing, 1962; Comeau, 1991; Mychajliw et GAUDIN AND BROOME.: Isolated petrosal of the extinct sloth Glossotherium tropicorum 61 al., 2020), likely due both to their proximity and intermittent land bridge connections between the island and the mainland. CONCLUSION The morphology of an isolated petrosal recov- ered from Pleistocene-aged tar pit deposits on the island of Trinidad strongly indicate a taxonomic provenance with the large bodied, terrestrial ex- tinct sloth species Glossotherium tropicorum. This represents the first published description of a my- lodontid sloth fossil from Trinidad, and represents a significant range extension for the species G. tropicorum, as well as only the second record of the well-known, widespread genus Glossotherium from outside mainland South America. It also rep- resents a late Cenozoic emigration of sloths into the Caribbean, distinct from the much earlier event that led to the endemic radiation of Antillean meg- alonychid sloths. Finally, this record provides fur- ther confirmation of the presence of savannah-like, open habitats on Trinidad during the Pleistocene, as part of the savannah corridor linking North and South America during the GABI. ACKNOWLEDGMENTS We thank Richard Hulbert and Jonathan Bloch (Florida Museum of Natural History, University of Florida, Gainesville, FL, USA) for the loan of the specimen that served as the subject of this report, as well as Gerry De Iuliis and Kevin Seymour (Royal Ontario Museum, Toronto, Canada) for their as- sistance with the loan of G. tropicorum specimens that served as critical comparative material. We also thank François Pujos and Alberto Boscaini, who served as reviewers for the manuscript, and the editor, Richard Hulbert, for their comments, which greatly improved the quality of this manu- script. This research was supported in part by the Bramblett Gift Fund and the Department of Biolo- gy, Geology & Environmental Science, University of Tennessee at Chattanooga. LITERATURE CITED Anderson, R. P. and C. O. Handley. 2001. A new species of three-toed sloth (Mammalia: Xenar- thra) from Panama, with a review of the genus Bradypus. Proceedings of the Biological Soci- ety of Washington 114(1):1-33. Blair, K. G. 1927. Insect remains from oil sand in Trinidad. Transactions of the Royal Entomo- logical Society of London 75(1):137–142. Bocquentin-Villanueva, J. 1979. Mammifères fos- siles du Pléistocène supérieur de Muaco, État de Falcón, Venezuela. Unpublished Ph.D. Dis- sertation. Université Pierre et Marie Curie, Pa- ris, France, 112 p. Boscaini, A., D. A. Iurino, G. Billet, L. Hautier, R. Sardella, G. Tirao, T. J. Gaudin, and F. Pujos. 2018. Phylogenetic and functional implica- tions of the ear region anatomy of Glossotheri- um robustum (Xenarthra, Mylodontidae) from the late Pleistocene of Argentina. The Science of Nature 105:28. doi:10.1007/s00114-018- 1548-y Boscaini, A., F. Pujos, and T. J. Gaudin. 2019. A reappraisal of the phylogeny of Mylodontidae (Mammalia, Xenarthra), and the divergence of mylodontine and lestodontine sloths. Zo- ologica Scripta 48(6):691–710. doi: 10.1111/ zsc.12376 Cartelle, C., and G. De Iuliis. 1995. Eremoth- erium laurillardi, the Panamerican late Pleis- tocene megatheriid sloth. Journal of Ver- tebrate Paleontology 15(4):830–841. doi: 10.1080/02724634.1995.10011265 Cartelle, C., and G. De Iuliis. 2006. Eremotherium laurillardi (Lund) (Xenarthra, Megatheriidae), the Panamerican giant ground sloth: taxon- omy aspects of the ontogenetic development of the skull and dentition. Journal of System- atic Paleontology 4(2):199–209. doi: 10.1017/ S1477201905001781 Cartelle, C., G. De Iuliis, A. Boscaini, and F. Pujos. 2019. Anatomy, possible sexual dimorphism, and phylogenetic affinities of a new mylodon- tine sloth from the late Pleistocene of inter- 62 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 58(3) tropical Brazil. Journal of Systematic Paleon- tology 17(23):1957–1988. doi:10.1080/14772 019.2019.1574406 Comeau, P. L. 1991. Geological events influencing natural vegetation in Trinidad. Living World Journal of the Trinidad and Tobago Field Natu- ralists Club 1991–1992:29–38. Dantas, M. A. T., A. Cherkinsky, H. Bocherens, M. Drefahl, C. Bernardes, and L. de Melo Fran- ça. 2017. Isotopic paleoecology of the Pleis- tocene megamammals from the Brazilian In- tertropical Region: Feeding ecology (d13C), niche breadth and overlap. Quaternary Science Reviews 170:152–163. doi:10.1016/j.quasci- rev.2017.06.030 De Iuliis, G., C. Cartelle, H. G. McDonald, and F. Pujos. 2017. The mylodontine ground sloth Glossotherium tropicorum from the late Pleis- tocene of Ecuador and Peru. Papers in Palaeon- tology 3(4):613–636. doi:10.1002/spp2.1088 De Iuliis G., A. Boscaini, F. Pujos, R. K. McAfee, C. Cartelle, L. J. S. Tsuji, and L. Rook. 2020. On the status of the giant mylodontine sloth Glos- sotherium wegneri (Spillmann, 1931) (Xenar- thra, Folivora) from the late Pleistocene of Ec- uador. Comptes Rendus Palevol 19(12):215- 232. Doi:10.5852/cr-palevol2020v19a12 Delsuc, F., M. Kuch, G. C. Gibb, E. Karpinski, D. Hackenberger, P. Szpak, J. G. Martínez, J. I. Mead, H. G. McDonald, R. D. E. MacPhee, G. Billet, L. Hautier, and H. N. Poinar. 2019. Ancient mitogenomes reveal the evolutionary history and biogeography of sloths. Current Biology 29(12):2031–2042. doi:10.1016/j. cub.2019.05.043 Gaudin, T. J. 1995. The ear region of edentates and the phylogeny of the Tardigrada (Mammalia, Xenarthra). Journal of Vertebrate Paleontology 15(3):672–705. doi:10.1080/02724634.1995.1 0011255 Gaudin, T. J. 2004. Phylogenetic relationships among sloths (Mammalia, Xenarthra, Tardi- grada): the craniodental evidence. Zoological Journal of the Linnean Society 140(2):255– 305. doi:10.1111/j.1096-3642.2003.00100.x Gazin, C. L. 1957. Exploration for the remains of giant ground sloths in Panama. Smithsonian Report for Panama 1956:341–354. Guth, C. 1961. La région temporale des édentés. Unpublished Ph.D. Dissertation. L’Université de Paris, Paris, France. 192 p. Harris, J. M. 2015. La Brea and Beyond: The Pale- ontology of Asphalt-Preserved Biotas. Natural History Museum of Los Angeles County Sci- ence Series 42:1–176. Iturralde-Vinent, M. A., and R. D. E. MacPhee. 1999. Paleogeography of the Caribbean re- gion: implications for Cenozoic biogeography. Bulletin of the American Museum of Natural Hisotry. 238:1-95. Kurtén, B., and E. Anderson. 1980. Pleistocene Mammals of North America. Columbia Uni- versity Press, New York, USA, 442 p. MacPhee, R. D. E., and M. A. Reguero. 2010. Re- interpretation of a middle Eocene record of Tardigrada (Pilosa, Xenarthra, Mammalia) from La Meseta Formation, Seymour Island, West Antarctica. American Museum Novitates 3689:1–21. doi:10.1206/703.1 McAfee, R. K. 2009. Reassessment of the cranial characters of Glossotherium and Paramylodon (Mammalia: Xenarthra: Mylodontidae). Zoo- logical Journal of the Linnean Society 155:885– 903. doi:10.1111/j.1096-3642.2008.00468.x McDonald, H. G., and G. De Iuliis. 2008. Fos- sil history of sloths. Pp. 39–55 in S. F. Viz- caíno and W. H. Loughry, eds. The Biology of the Xenarthra. University Press of Florida, Gainesville, USA. McDonald, H. G., J. M. Harris, and E. Lindsey. 2015. Introduction. Pp. 1–4 in J. M. Harris, ed. La Brea and Beyond: The Paleontology of Asphalt-Preserved Biotas. Natural History Museum of Los Angeles County Science Se- ries, 42, Los Angeles, USA. McKenna, M.C., and S.K. Bell. 1997. Classifica- tion of Mammals Above the Species Level. Columbia University Press, New York, USA, 631 p. Michajliw, A. M., R. S. Mohammed, K. A. Rice, GAUDIN AND BROOME.: Isolated petrosal of the extinct sloth Glossotherium tropicorum 63 A. B. Farrell, A. D. Rincón, R. McAfee, H. G. McDonald, and E. L. Lindsey. 2020. The bio- geography of “breas”: contextualizing the ta- phonomy, ecology, and diversity of Trinidad’s asphaltic fossil record. Quaternary Science Reviews 232:106179. doi:10.1016/j.quasci- rev.2020.106179 Ogg, J. G., G. Ogg, and F. M. Gradstein. 2016. A Concise Geologic Time Scale. Elsevier Press, New York, USA, 234 p. Patterson, B., W. Segall, W. D. Turnbull, and T. J. Gaudin. 1992. The ear region in xenar- thrans (=Edentata, Mammalia). Part II. Sloths, Anteaters, Palaeanodonts, and a Miscella- ny. Fieldiana, Geology new series 24:1–79. doi:10.5962/bhl.title.3466 Philippon, M., J.-J. Cornée, P. Münch, D. J. J. van Hinsbergen, M. BouDagher-Fadel, L. Gailler, L. M. Boschman, F. Quillevere, L. Mon- theil, A. Gay, J. F. Lebrun, S. Lallemand, L. Marivaux, P.-O. Antoine, with the GARANTI Team. 2020. Eocene intra-plate shortening responsible for the rise of a faunal pathway in the northeastern Caribbean realm. PLoS one 15(10):e0241000. doi:10.1371/journal. pone.0241000 Pielou, E.C. 2008. After the Ice Age: The Return of Life to Glaciated North America. University of Chicago Press, Chicago, USA, 366 p. Presslee, S., G. J. Slater, F. Pujos, A. M. Forasiepi, R. Fischer, K. Molloy, M. Mackie, J. V. Olsen, A. Kramarz, M. Taglioretti, F. Scaglia, M. Lez- cano, J. L. Lanata, J. Southon, R. Feranec, J. Bloch, A. Hajduk, F. M. Martin, R. Salas Gis- mondi, M. Reguero, C. de Muizon, A. Green- wood, B. T. Chait, K. Penkman, M. Collins, and R. D. E. MacPhee. 2019. Palaeoproteomics resolves sloth relationships. Nature Ecology & Evolution 3:1121–1130. doi:10.1038/s41559- 019-0909-z Pujos, F., T. J. Gaudin, G. De Iuliis, and C. Cartelle. 2012. Recent advances on variability, morpho- functional adaptations, dental terminology, and evolution of sloths. Journal of Mamma- lian Evolution 19(3):159–169. doi:10.1007/ s10914-012-9189-y Pujos, F., G. De Iuliis, and C. Cartelle. 2016. A paleogeographic overview of tropical fossil sloths: towards an understanding of the origin of extant suspensory sloths? Journal of Mam- malian Evolution 24(1):19–38. doi:10.1007/ s10914-016-9330-4 Resar, N. A., J. L. Green, and R. K. McAfee. 2013. Reconstructing paleodiet in ground sloths (Mammalia, Xenarthra) using dental mi- crowear analysis. Kirtlandia 58:61–72. Román-Carrión, J. L., L. Brambilla. 2019. Com- parative skull osteology of Oreomylodon we- gneri (Xenarthra, Mylodontinae): defining the taxonomic status of the Ecuadorian endemic mylodontid. Journal of Vertebrate Paleontol- ogy 39(4):e1674860. doi:10.1080/02724634.2 019.1674860 Sánchez Chillón, B., J. L. Prado, and M. T. Alber- di. 2003. Paleodiet, ecology, and extinction of Pleistocene gomphotheres (Proboscidea) from the Pampean Region (Argentina). Coloquios de Paleontología 1:617–625 Schaub, S. 1935. Säugetierfunde aus Venezuela und Trinidad. Abhandlungen der Schweizerischen Palaeontologischen Gessellschaft 55:1–21. Segall, W. 1970. Morphological parallelisms of the bulla and auditory ossicles in some insectivores and marsupials. Fieldiana, Zoology 51:169–205. Steadman, D. W., P. S. Martin, R. D. E. MacPhee, A. J. T. Jull, H. G. McDonald, C. A. Woods, M. Iturralde–Vinent, and G. W. L. Hodgins. 2005. Asynchronous extinction of late Quaternary sloths on continents and islands. Proceedings of the National Academy of Sciences 102:11763– 11768. doi:10.1073/pnas.0502777102 Varela, L., P. S. Tambusso, H. G. McDonald, and R. A. Fariña. 2018. Phylogeny, macroevolu- tionary trends and historical biogeography of sloths: insights from a Bayesian morphological clock analysis. Systematic Biology 68(2):204– 218. doi:10.1093/sysbio/syy058 Vizcaíno, S. F., G. H. Cassini, J. C. Fernicola, and M.S. Bargo. 2011. Evaluating habitats and feeding habits through ecomorphological fea- 64 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 58(3) tures in glyptodonts (Mammalia, Xenarthra). Ameghiniana 48(3):305–319. doi:10.5710/ AMGH.v48i3(364) Webb, S. D. 1991. Ecogeography and the Great American Interchange. Paleobiology 17(3):266–280. Wible, J. R. 2010. Petrosal anatomy of the nine- banded armadillo, Dasypus novemcinctus Lin- naeus, 1758 (Placentalia: Xenarthra: Dasypo- didae). Annals of Carnegie Museum 79:1–28. doi:10.2992/007.079.0101. Wing, E. S. 1962. Succession of mammalian fau- nas on Trinidad, West Indies. Unpublished M.S. thesis. University of Florida, Gainesville. 76 p. Woodburne, M. O., F. J. Goin, M. Bond, A. A. Car- lini, J. N. Gelfo, G. M. López, A. Iglesias, and A. N. Zimicz. 2014. Paleogene land mammal faunas of South America; a response to global climatic changes and indigenous floral diversi- ty. Journal of Mammalian Evolution 21(1):1– 73. doi:10.1007/s10914-012-9222-1