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Anatomical features of the humerus, ulna and radius of Plesiotypotherium achirense. a-b, Right humerus (paratype, MNHN ACH 18) in cranial and distal views, respectively; c, Right ulna (MNHN-Bol-V 12687) in cranial view; d, Left radius (paratype, MNHN ACH 18) in caudal view. Abbreviations: anc. proc, anconeus process; bicc. tuber, biccipital tuberosity; cap.rad, caput radii; cap.ul, caput ulnae; cap, capitulum; circ.art, circumferentia articularis of the radius; circ.art, circumferentia articularis of the ulna; cor. pro, coronoid process (processus coronoideus mediallis); crist.hum, crista humeri; crist.suprac, crista supracondylaris lateralis (epicondylar crest); crist.t.maj, crista tubercularis majoris; ent.for, entepicondylar foramen; epic.med, epicondylus medius (entepicondyle); fac.art.car, facies articularis carpea; for.supth, foramen supratrochlear; fov.cap.rad, fovea capitis radii (radial notch); inc.rad, incisura radialis; inc.rad, incisura ulnaris; lin.m.tric, linea m. tricipitis; ol, olecranon; sty.proc, styloid process; tr.hum, trochlea humeri; tr.rad, trochlea radii; tub.del, tuberositas deltoidea; tub.maj, tuberculum majus; tub.min, tuberculum minor; tub.ol, tuber olecrani (proximal tubercle); tub.t.maj, tuberositas teres major
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In the present work, we provide muscular reconstruction
and we infer functional properties of the forelimb
of Plesiotypotherium achirense, a fossil mesotheriid
notoungulate from the late Miocene of Achiri (Bolivia). This
locality has yielded the widest sample ever available for the
forelimb of a mesotheriid. In addition, we propose a qualitative
co...
Citations
... Among the potential creators of these structures have been suggested: 1) mesotheres (Late Miocene of La Pampa Province . (Cardonatto and Melchor, 2018; which would also be given by its appendiculate morphofunctional structures and by its inferred semifossorial faculty (including M. cristatum; Shockey et al., 2007;Fernández-Monescillo et al., 2018); or 2) Scelidotherium, also present in Corralito site (see Frenguelli, 1921;Vizcaíno et al., 2001); but it is not exclusive that both could produce these burrows. ...
We present a detailed analysis of the craniomandibular and dental remains of Mesotherium cristatum, the qua-ternary mesotheriid typotherid notoungulate, from Corralito, Santa María Department, Cordoba Province. This population represents the final lineage of Typotheria during middle Pleistocene, Post-Ensenadan Age (>220 ± 13 ka). We compared these new craniomandibular and postcranial samples from Corralito with those from Toscas del Río de La Plata, as well as other localities in the province of Buenos Aires dating to the Ensenadan Age 1.98-0.4 Ma). Our investigation reveals a substantial decline in the size and body mass of the last known population of M. cristatum during the Bonaeran Age period, before its extinction. This occurrence, hitherto un-recorded in any prior South American Land Mammal Age leading up to extinction, might be attributed to the climatic and abiotic changes of the Pleistocene. These changes notably caused a marked reduction in the pale-obiogeographical distribution area ofM. cristatum during the Middle Pleistocene. This size and body mass reduction, possibly an outcome of compelled reproductive isolation, is situated against the context of global cooling and heightened predatory pressures. Moreover, our analysis unveiled distinctive taxonomic attributes specific to this taxon, we compare dental size and find a preliminary evidence of an accelerated tooth replacement pattern. Furthermore, we have effectively updated the faunal composition information of the Corralito deposit, elucidating previous biostratigraphic inferences that had led to the belief of Corralito being an Ense-nadan Age site. This adjustment impacts the first appearance datum (FAD) of the Neolicaphrium recens proter-otheriid litoptern, younger than previously estimated and revised Bonaerian-Lujanian. Finally, this study provides insights into the biological analysis of the iconic species M. cristatum, prevalent in the South American quaternary of the Pampean region. It unreveils new faunal features specific to the Pampean region, shedding light particularly on the lesser-explored western area. These findinngs provide crucial insight into the ever-evolving ecosystem dynamics during the Middle Pleistocene.
... This depression is present along the entire diapophysis of the ulna to the proximal end. This depression may have been for a ligamentous attachment between the radius and ulna, and/or for the insertion of the abductor pollicis longus muscle (Fern andez-Monescillo et al., 2018;Jenkins, 1971). The distal end of the ulna is not preserved. ...
Diarthrognathus broomi is a transitional taxon between non-mammaliaform cynodonts and Mammaliaformes that occurred during the Late Triassic to Early Jurassic. All known specimens of Diarthrognathus represent juveniles, and the postcrania have not been thoroughly described. The palatal, basicranial and postcranial elements of the referred specimen NMQR 1535 are described here for the first time using 3D reconstructions generated from X-ray micro-computed tomography (μCT) data. The presence of a large interpterygoid vacuity, open medial suture between the vomers and medially unossified secondary palate all support the interpretation that NMQR 1535 is a juvenile. In addition, Diarthrognathus uniquely possesses "suborbital" vacuities, which distinguishes it from every other known cynodont. The presence of an ossified olecranon process, among other features, suggests that Diarthrognathus may have been a scratch-digger. The postcranial skeleton of Diarthrognathus appears to be more plesiomorphic than tritylodontids, Brasilodon and other tritheledontids as, among other traits, it retains amphicoelous vertebrae. However, this taxon also displays synapomorphies with the more derived cynodonts, such as the mammalian pattern of neuro-central ossification and possible absence of an ectepicondylar foramen.
... Many notoungulates are known from complete or nearly complete skeletons (e.g., Sinclair 1909;Scott 1912;Riggs 1937;Simpson 1945;Chaffee 1952;Stirton 1953;Shockey 1997;Cerdeño et al. 2012), and many others are known from well-preserved skulls and/or postcrania (e.g., Simpson 1948Simpson , 1967Bocchino de Ringuelet 1957;Villarroel 1974a;Cerdeño and Contreras 2000;Hitz et al. 2000;Croft et al. 2003;Shockey and Anaya 2008;Billet et al. 2009;Shockey et al. 2012;Vera 2012;Guérin and Faure 2013;Giannini and García-López 2014;Fernández-Monescillo et al. 2022). The abundance of notoungulate remains has made it possible for researchers to study many aspects of their paleobiology, particularly within the past decade, which has provided new insights into their habits and habitats (e.g., Cassini and Vizcaíno 2012;Cassini et al. 2012aCassini et al. , b, 2017Gomes Rodrigues et al. 2017;Fernández-Monescillo et al. 2018;Sosa and García-López 2018;Ercoli et al. 2019Ercoli et al. , 2021aLorente et al. 2019;Croft and Lorente 2021). Nevertheless, because there are no extant notoungulates, correlations between anatomy and ecology are difficult; in some cases, different analyses have reached in disparate or even contradictory conclusions about their paleobiology. ...
... By contrast, Pleistocene Toxodon platensis (similar to Nesodon imbricatus; Fig. 1, lower left) was a large-headed, graviportal megamammal (Bond 1999;MacFadden 2005). Even within this great range of body size diversity, there was also significant ecomorphological diversity, including: long-necked members of Leontiniidae (e.g., Scarritia canquelensis and Taubatherium paulacoutoi ;Chaffee 1952;Couto-Ribeiro 2015); fossorial, wombat-like mesotheriids Fernández-Monescillo et al. 2018); the elongate, ferretlike Interatherium spp. (Sinclair 1909;Fig. ...
Body mass (BM) is a fundamental variable for many paleobiological investigations that is challenging to accurately infer for species that lack living representatives and/or close morphological analogs. This study explores this issue using notoungulates, a diverse group of extinct South American herbivorous mammals with an extensive fossil record. We use a new dataset of 1,900+ extant mammal species (from ~80,000 specimens) to estimate notoungulate BM based on head-body length and a published dataset of 400+ species (~2,100 specimens) to estimate BM based on occipital condyle width. Condylobasal length, stylopod diameter and circumference, and neck length data are used to explore factors that can confound BM predictions. We estimate the following BM ranges for 10 osteologically well-characterized species and calculate similar ranges for 30 others known from less complete remains: Toxodontia: Thomashuxleya externa (80–120 kg), Homalodotherium cunninghami (250–350 kg), Scarrittia canquelensis (450–550 kg), Adinotherium ovinum (75–90 kg), Nesodon imbricatus (350–400 kg), and Toxodon platensis 1,000–1,200 kg); Typotheria: Interatherium robustum (1.9–2.0 kg), Miocochilius anomopodus (9–14 kg), Protypotherium australe (3.5–4.0 kg), and Pachyrukhos moyani (1.2–1.6 kg). We suggest that species such as these can be used as “calibration points” when inferring BM of species known from more limited remains. Discrepancies between our estimates and previously-published studies are primarily due to the distinctive craniodental morphology of notoungulates and the robust limb bones of toxodontians. There is significant, non-random error correlated with body habitus (i.e., being relatively robust or gracile) in many variables traditionally used to estimate BM, including femur circumference, and new methods are needed to compensate for this.
... Typotheria includes species with some appendicular locomotor features reminiscent of modern cursorial taxa, such as some interatheriids and hegetotheriids (Cassini et al., 2012b;Croft & Anderson, 2008;Sinclair, 1909;Stirton, 1953), although a recent study did not support the presence of clear cursorial adaptations in this group (Croft & Lorente, 2021). The appendicular skeleton of Mesotheriidae has semifossorial traits (Shockey et al. 2007;Fernández-Monescillo, et al. 2018). Some of the families within the suborder Typotheria have rodent-like craniomandibular features (Bond et al., 1995;Ercoli et al. 2019; F. Ameghino, 1889;Reguero & Prevosti, 2010;Sinclair, 1909). ...
Mesotheriid taxonomy for Monte Hermoso, Buenos Aires province, Argentina is extremely complex, with much of the controversy centered on the Late Miocene–Pliocene mesotheriine notoungulate type species Pseudotypotherium pulchrum, which is a subjective junior synonym of P. exiguum. Confusion around P. exiguum intraspecific variation is exacerbated by specimens of the Pleistocene taxon Mesotherium cristatum originally defined in Toscas del Río de La Plata. As a result, remains of Monte Hermoso mesotheres have been referred to six species and four genera (Typotherium, Pseudotypotherium, Xenotherium, and Typotheriodon) during the past 100 + years. The current consensus is that Pseudotypotherium is the correct genus for Monte Hermoso mesotheres, but detailed analyses of variation, especially ontogenetic, have been lacking. We rectify that deficiency in this work through bibliographic and firsthand study of type materials and comparison of molar size (PCA of linear dimensions) and i1 ontogenetic variation (via CT) using a broad ontogenetic series. We conclude that the variation observed in Monte Hermoso mesotheres is consistent with ontogenetic and individual variation within a single species. As previously suggested, Pseudotypotherium (=Typotherium) exiguum is the valid senior synonym for Monte Hermoso mesotheres. We provide a detailed diagnosis and description of P. exiguum, including a rather complete ontogenetic series, the first for any species of Pseudotypotherium.
... Because several bones were fragmented or lacked one or both epiphyses, full reconstructions of the bone material was based on the comparison with more complete skeletons of closely related mesotheriines (e.g. Plesiotypotherium [58,60,61]). This allowed us to ensure that our histological samples are come from the midshaft. ...
he Miocene Caragua fossil fauna in northern Chile contains a considerable number (7) of articulated partial skeletons tentatively assigned to Caraguatypotherium munozi (Notoungu-lata, Mesotheriidae), which presents up to 40% body size difference. Since either inter- and intra- specific wide size range has been observed in the Mesotheriidae family in general, we wanted explore the ontogenic stage signature of the sample, by carrying out the first comprehensive paleohistological description of the appendicular system in Notoungulata.
Results show that: 1) they can be classified as subadults and adults, based on the presence of bone tissues typical of ceased somatic growth; 2) there is a notorious inter-skeletal variation on bone growth rates (skeletal modularity), particularly, the humerus showed a slower diameter growth and less remodelling than the femur, resulting as a better element for ontogenetic analyses; 3) marked cyclical growth is observed, characterised by fast early ontogenic continuous growth, and subsequent fast/slow stratified bone tissue layering. In general, such growth pattern suggests that C. munozi had a similar ontogenetic growth process as other modern mammals, that it should also be influenced by other sex-related, ecological and environmental factors. Likely related to the presence of rapid climatic variations, due to orogenic uplift and concomitant re-organization of the drainage processes along the western tectonic front of the Central Andes at that time.
... 4). Published data of mesotheres are available only for Trachytherus, Plesiotypotherium and Mesotherium, in which the humeri are robust, with a sigmoid shaft, massive and laterally extended deltopectoral crest, a more projected medial epicondyle and entepicondyle, and a laterally wellextended crest (Fernández-Monescillo et al., 2017). These features are clearly different from the humeri here attributed to Pseudotypotherium based on the associated dentition. ...
... (Fernández-Monescillo et al., 2017; fig. 8). ...
A joint expedition between the Museum of Comparative Zoology of Harvard University (Cambridge, Massachusetts, USA) and the Museo Argentino de Ciencias Naturales (Buenos Aires, Argentina) explored outcrops in west-central Argentina during autumn of 1958. The team led by Alfred S. Romer collected fossils from several Cenozoic outcrops from Mendoza, San Juan, and La Rioja provinces. Some of the recovered fossils were previously published, including gastropods, birds, turtles, and mammals. However, other specimens, which belong to the Vertebrate Paleontology collection at the Museum of Comparative Zoology, remained unknown and even uncatalogued until the present contribution. Here, we present this peculiar collection for the first time, providing an updated taxonomic list of the vertebrate remains. Based on the studied material, we identified 1) Glyptodontidae (cf. Propalaehoplophorus), Dasypodidae (Stenotatus sp.), Mesotheriidae (cf. Altitypotherium), Macraucheniidae (Cramaucheniinae gen. et sp. indet.) and Rodentia indet. in the Aisol Fm.; 2) Megatheriidae (Pyramiodontotherium sp.) and Macraucheniidae (Macraucheniinae gen. et sp. indet.) in the Tunuyn Fm.; 3) Dasypodidae indet. in the Mario Fm.; 4) Hegetotheriidae (Hemihegetotherium sp., Pachyrukhinae gen sp. indet., Paedotherium sp.) and Rodentia indet. in the Pilona Fm.; and 5) Cingulata indet., Mesotheriidae (Pseudotypotherium sp.), Hegetotheriidae (Tremacyllus sp.), Chinchiliidae indet., and Hydrochoeridae indet. in the Huachipampa Fm. The reports of the Romer collection from Argentina allow the establishment of biochronological correlations between the lesser-known faunas from west-central Argentina and faunas from other areas of South America.
... In addition, descriptions of non-mammaliaform postcrania have greatly increased in number in recent years (Liu et al., 2017;Gaetano et al., 2017Gaetano et al., , 2018Guignard et al., 2018Guignard et al., , 2019aButler et al., 2019;Mocke et al., 2019), thus enabling more useful comparisons. Synchrotron X-ray computed tomography (SRCT) has proven effective for the digital, non-destructive preparation of fossil specimens for two main reasons: first, it uniquely provides a powerful beam that penetrates rocks that most common Xray sources cannot (e.g., most medical and laboratory setups); and second, properties of the synchrotron beam facilitate the use of phase contrast imaging which allows for visualization of internal structures that would otherwise be out of reach (Tafforeau et al., 2006;Tafforeau and Smith, 2008;Carlson et al., 2011;Fernandez et al., 2013Fernandez et al., , 2015Benoit et al., 2016aBenoit et al., , 2017bChapelle et al., 2019Chapelle et al., , 2020Radermacher et al., 2021). With the aid of synchrotron scanning, we provide the first detailed descriptions of the postcranial anatomy and dentition (including dental replacement) of Lumkuia fuzzi. ...
... The medial aspect of the ulna is poorly preserved as the surface appears jagged (Fig. 8H). The anterior face of the ulnar crest seems excavated by a shallow fossa, likely for ligamentous attachment with the radius (Jenkins, 1971) and insertion of the abductor pollicis longus muscle (Fernández-Monescillo et al., 2018). The large interosseous ligament attachment surface area and the absence of a facet for movements between the radius and ulna suggest that the two bones were overlapped in life and functioned as a single unit. ...
Lumkuia fuzzi is a small non-mammalian cynodont from the Middle Triassic of South Africa. It has traditionally been phylogenetically identified as a basal Probainognathia, but some studies place it more basally as the sister-group to Eucynodontia. Lumkuia is known from a single specimen comprising a skull and partial skeleton. Only the skull has been thoroughly described. Here we use synchrotron X-ray computed tomography to describe the dental series and postcranial skeleton of Lumkuia. The shoulder girdle, forearm, manual phalanges, partial vertebral column, and ribs are described. To assess the effect of these new observations on the phylogenetic position of Lumkuia, the scoring of this taxon is updated and new characters are added to two previous analyses, one supporting Lumkuia as a Probainognathia and the other in which the taxon is usually retrieved as a basal Eucynodontia. Our phylogenetic analyses all unambiguously support the position of Lumkuia as a basal Probainognathia. The most commonly retrieved synapomorphies shared by Lumkuia and the probainognathians are cranial (absence of an ectopterygoid and pineal foramen), postcranial (the procoracoid does not contribute to the glenoid fossa), and palaeoneurological (reduction of the external nasal ramus of the maxillary canal, presence of a cochlear canal) characters. The degree of skeletal ossification and stages of dental replacement and wear support that the specimen is a subadult. The forelimbs were adapted to sprawling and occasional scratch-digging, thus suggesting a facultative fossorial ecology for Lumkuia.
... Among the more distinctive typotheres are members of the family Mesotheriidae. This family includes the largest typotheres, many of which were apparently semifossorial (Shockey et al. 2007;Fernández-Monescillo et al. 2018). Mesotheriidae includes the monogeneric Trachytheriinae (Late Oligocene; Billet et al. 2008;Shockey et al. 2016) and the welldiversified Mesotheriinae (Miocene-Pleistocene; Francis 1960Francis , 1965Croft et al. 2004;Paz et al. 2011). ...
We report systematic conclusions based on critical analyses of previous taxon diagnoses and systematic revisions of the Early-Middle Pleistocene mesotheriine notoungulate Mesotherium cristatum Serres 1867, from Buenos Aires province, Argentina. Mesotherium cristatum is a key taxon, as it is the guide species of the Ensenadan Age (Early-Middle Pleistocene), it typifies the “Mesotherium cristatum biozone”, and it is the last member of the Typotheria lineage. The taxonomic history and its successive revisions are especially complex due to the lack of recognition of the ontogenetical variation for this taxon, often considered as intrageneric variations (Typotherium, Typotheridion) or also as inter-specific variation (a total of seven different species have been named). In fact, the taxonomic complexity was increased due to misidentification with specimens or taxa originally defined in the late Pliocene (i.e., Monte Hermoso, Montehermosan SALMA). We conclude that the variation among the numerous purported Early-Middle Pleistocene mesotheriine taxa is consistent with intraspecific and ontogenetic variation in a single species, here recognised as M. cristatum. This puts an end to the supposed sympatry of two other species (Mesotherium maendrum and Typotherium pachygnatum) with M. cristatum; and also, with other species scarcely considered (Typotherium angustirostrum and Bravardia pampaea). Accordingly, Mesotherium is a monotypic genus.
... For mesotheriid notoungulates, selective pressures related to a fossorial or semifossorial lifestyle [74,122] were likely greater than those favoring efficient or rapid locomotion in open habitats. Larger Neogene typotheres such as mesotheres may have had limb proportions similar to some extinct North American oreodonts (Merycoidodontidae), which were not included in the analysis of Janis and Wilhelm [28] due to their digitigrade stance. ...
During the Neogene, many North American ungulates evolved longer limbs. Presumably, this allowed them to move more efficiently or quickly in open habitats, which became more common during this interval. Evidence suggests that open habitats appeared even earlier in South America, but no study to date has investigated whether the ungulate-like mammals of South America (South American native ungulates or SANUs) evolved similar limb adaptations. We analyzed limb elongation in the two predominant SANU groups, notoungulates and litopterns, by compiling genus-level occurrences from the late Oligocene to the Pleistocene and calculating metatarsal/femur ratio (Mt:F). None of the groups or subgroups we analyzed show a pronounced increase in Mt:F across this interval, with the possible exception of proterotheriid litopterns. Proterotheriids are thought to have inhabited forested environments rather than open ones, which raises questions about the selective forces responsible for limb elongation in ungulates. Conversely, notoungulates, which are traditionally thought to have lived in open habitats, show no strong trend of increasing Mt:F across this interval. Our study suggests that the macroevolutionary trend of limb elongation in ungulate-like mammals is not universal and is highly influenced by the evolutionary affinities of the groups being analyzed.
... The glyptodontid Hoplophractus has been described as a bulkfeeding inhabitant of moderately open habitats (Vizcaíno et al. 2011). Typotheriopsis (Notoungulata) is considered as an inhabitant of open, dry areas, with fossorial abilities and masticatory specialisations for the consumption of hard food items (Fernández-Monescillo et al. 2018;Ercoli & Armella 2021). Paedotherium was a small terrestrial herbivorous that resembles extant leporids, probably adapted to open and semi-arid habitats (Cerdeño & Bond 1998;Reguero et al. 2007;Tomassini et al. 2017 and references therein). ...
Echimyidae is the most widely diversified family among hystricognath rodents, both in the number of species and variety of lifestyles. In the Patagonian Subregion of southern South America, extinct echimyids related to living arboreal species (Echimyini) are recorded up to the middle Miocene, whereas all the known southern fossils since the late Miocene are linked to terrestrial and fossorial lineages currently inhabiting the Chacoan open biome in eastern South America. In this work, we describe a new genus of echimyid rodent, Paralonchothrix gen. nov., from the late Miocene of northwestern Argentina and western Brazil. Its single recognised species, Paralonchothrix ponderosus comb. nov., is represented by two hemimandibles. One of them comes from a level of Loma de Las Tapias Formation, underlying a tuff dated at 7.0 ± 0.9 Ma (Huayquerian age, late Miocene); the other specimen comes from the 'Araucanense' of Valle de Santa María (type locality, Huayquerian age, late Miocene). A phylogenetic analysis linked Paralonchothrix to Lonchothrix, both being the sister group to Mesomys. Thereby, for the first time, an echimyid linked to living Amazonian arboreal clades is recognised for the late Miocene of southern South America. Paralonchothrix gen. nov. thus represents an exceptional record that raises the need to review the postulated evolutionary pattern for echimyids recorded at high latitudes since the late Miocene. The new genus provides a minimum age (ca.7 Ma) in the fossil record for the divergence between Mesomys and Lonchothrix. The palaeoenvironmental conditions inferred for the late Miocene in western and northwestern Argentina suggest savanna-type environments, with areas with more closed woodlands in peri-Andean valleys. The record of Paralonchothrix gen. nov. supports the hypothesis that this area would have maintained connections with tropical biomes of northern South America during the late Miocene.
