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Orretherium tzen gen. et sp. nov. (CPAP-5007, holotype). (a–c) Partial left dentary with p2-p3 and m1-m3 in occlusal (a), labial (b) and medial (c) views. Drawings made by A.G.M. ac accessory cusp, coc coronoid crest, dc distal cingulum, de dentine, en enamel, maf masseteric fossa, mc mesial cingulum, mf mental foramen, med metaconid, pad paraconid, prd protoconid, rm retromolar space. Scale bar: 5 mm.
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In the last decades, several discoveries have uncovered the complexity of mammalian evolution during the Mesozoic Era, including important Gondwanan lineages: the australosphenidans, gondwanatherians, and meridiolestidans (Dryolestoidea). Most often, their presence and diversity is documented by isolated teeth and jaws. Here, we describe a new meri...
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... To analyse the phylogenetic affinities of Patagomaia chainko, it was scored into three different comprehensive mammalian data matrices 13,59,60 . The incomplete nature of the holotype specimen, plus the fact that most of these datasets heavely rest on skull and teeth information, we were able to score just a small number of characters (less than 2.5%) for Patagomaia. ...
Theria represent an extant clade that comprises placental and marsupial mammals. Here we report on the discovery of a new Late Cretaceous mammal from southern Patagonia, Patagomaia chainko gen. et sp. nov., represented by hindlimb and pelvic elements with unambiguous therian features. We estimate Patagomaia chainko attained a body mass of 14 kg, which is considerably greater than the 5 kg maximum body mass of coeval Laurasian therians. This new discovery demonstrates that Gondwanan therian mammals acquired large body size by the Late Cretaceous, preceding their Laurasian relatives, which remained small-bodied until the beginning of the Cenozoic. Patagomaia supports the view that the Southern Hemisphere was a cradle for the evolution of modern mammalian clades, alongside non-therian extinct groups such as meridiolestidans, gondwanatherians and monotremes.
... This is due to the fact that the exchange between Gondwana (South America, Africa, Australia) and the Northern Hemisphere (North America, Europe, Asia) was possible during the Jurassic, and possibly extending into the Early Cretaceous (Kunzmann 2007). However, the presence of temporary land bridges, for example, across the Scotia Arc, would have facilitated intercontinental dispersal of organisms between the margins of West Gondwana and West Antarctica (Martinelli et al. 2021). ...
The phylogeny of the genus Pelecorhynchus Macquart (Diptera: Pelecorhynchidae) was analyzed using three genes, cytochrome oxidase I, 28S ribosomal DNA, and CAD5, with 112 morphological characteristics. A total of 59 specimens (13 outgroups and 46 ingroups) were included in the analysis. The monophyly of Pelecorhynchidae was recovered under all analyses, with Glutops Burgess as the sister group of Pelecorhynchus s.l., while Pseudoerinna jonesi (Cresson) was the sister group. Within “Pelecorhynchus” there are three main clades with unresolved affinities. Clade I was formed by P. personatus (Walker), P. vulpes (Macquart), P. penai Pechuman and P. kroeberi (Lindner), a well-supported clade. Clade II corresponds to the set of species of “Chilean Pelecorhynchus”, conformed to P. biguttatus (Philippi), P. toltensis Llanos & González, P. elegans (Philippi), P. xanthopleura (Philippi), P. hualqui Llanos & González, and P. longicauda (Bigot), a well-supported clade. Clade III is represented exclusively by P. fulvus Ricardo, which has an exclusively Australian distribution. The monophyly of P. fulvus and its nomenclature remain an open question, as only a single species of this taxon was included. Our study demonstrated that the concept of Pelecorhynchus should be revisited. Therefore, we restore Coenura Bigot, 1857 to generic status for part of the southern South American species of “Pelecorhynchus” conformed by the species C. biguttata, C. elegans, C. hualqui, C. longicauda, C. toltensis, and C. xanthopleura which are monophyletic, supported by molecular and morphological data, and consistent with a Chilean distribution.
... The earliest fossil of the Paurodontidae, from the Balabansai Formation of Kyrgyzstan, is of Callovian age, Middle Jurassic (Martin and Averianov 2010), and the family extends to the Late Jurassic (Simpson 1929;Krebs 1991Krebs , 2000Averianov and Martin 2015). It should be noted that in some recent analyses, the paurodontids have turned out to be paraphyletic (Rougier et al. 2012;Averianov et al. 2013;Wible and Rougier 2017; although see Martinelli et al. 2021). The earliest fossils of the family Dryolestidae are from the Middle Jurassic Berezovsk site of Siberia (Averianov et al. 2014) and the Late Bathonian, Middle Jurassic Forest Marble Formation of Great Britain (Freeman 1976(Freeman , 1979. ...
... However, a majority of the recent re-analyses of their relationships placed meridiolestidans and some paurodontids (with exception of Henkelotherium) as an independent clade from dryolestids (Rougier et al. 2012;Averianov et al. 2013;O'Meara and Thompson 2014;Wible and Rougier 2017), rendering paurodontids as a paraphyletic grouping. Other phylogenetic analyses with a smaller taxonomic sample still recognize the Paurodontidae as a clade (e.g., Martinelli et al. 2021), or recognize meridiolestidans as a group nested in the spalacotherioid clade, not related to dryolestidans (Averianov et al. 2013). ...
... Eight endemic genera of meridiolestidans are known from the Cretaceous and Cenozoic of South America (Martinelli et al. 2021). The genus Peligrotherium is known from the Paleocene of Argentina, and the genus Necrolestes from the Miocene of Argentina is also considered to be a meridiolestidan (Rougier et al. 2012;Chimento et al. 2012;Wible and Rougier 2017). ...
Henkelotherium guimarotae Krebs 1991 is an important Jurassic mammal for understanding therian evolution. We are presenting a new study of extensive, previously undescribed, mandibles and dentitions. The revised dental formula is: I4? or 5?/i4, C1/c1, P4/p4, M6/m7. The canine and premolars show an alternate replacement that ends with M4/m4 eruption, and is followed by a late sequential eruption of the last three lower (m5-7) and last two upper (M5-6) molars. The lower premolars erupted in the following order: p1 → p3 → p2 → p4, and the canine erupted most probably shortly before p4. The timing of the premolar replacement before the late molar eruption is similar to that of Dryolestes leiriensis, and is a characteristic of dryolestidans. Henkelotherium lower molars have subequal roots, a plesiomorphy of non-dryolestidan mammals, and the upper molars are supported by a strong, curved lingual root; a derived character. In the upper molars, the postvallum wear surface is contiguous to the parastyle wear surface of the succeeding molar, which differs from dryolestids. The parastylar lobe of the succeeding molar, and the postvallum of the preceding molar, are imbricated, and can develop strong, continuous wear surfaces, matching the prevallid crest of the lower molar. Henkelotherium differs from dryolestids in having an inflected, shelf-like mandibular angular process with a foramen. This large sample of Henkelotherium shows a significant variation gradient along the molar series, with the strongest wear occurring only in two to three consecutive molars. The extraordinarily long molar row is correlated with the late growth of jaws; and the jaw with late addition of molars sustained an effective mastication, much longer in older adults of dryolestidans than in other Mesozoic stem therians. The late eruption of several more molars after completion of antemolar replacement suggests that dryolestidans had either a longer-lived life, or slower life-history traits, or a combination of both, than crown therians.
... As far as mammals is concerned, the same fossil spot yielded a molar of the gondwanatherian Magallanodon baikashkenke 9 and isolated caudal vertebrae regarded as Mammalia incertae sedis 8 . From almost equivalents levels belonging to the Dorotea Formation (Valle del Río de las Chinas, southern Chile), remains of Magallanodon and the meridiolestidan Orretherium have been reported 10,11 . ...
... The new discovery expands the list of mammals documented in the Chorrillo and equivalent Dorotea formations of southern South America, adding the Monotremata to the assemblage of non-therian mammals (i.e., gondwanatherians and meridiolestidan dryolestoids [9][10][11]13 ). Remarkably, monotremes are absent from the extensively sampled Late Cretaceous localities of northern and central Patagonia 2,29,30 . ...
Monotremata is a clade of egg-lying mammals, represented by the living platypus and echidnas, which is endemic to Australia, and adjacent islands. Occurrence of basal monotremes in the Early Cretaceous of Australia has led to the consensus that this clade originated on that continent, arriving later to South America. Here we report on the discovery of a Late Cretaceous monotreme from southern Argentina, demonstrating that monotremes were present in circumpolar regions by the end of the Mesozoic, and that their distinctive anatomical features were probably present in these ancient forms as well.
... Recent studies have established a well-constrained stratigraphic framework for the valley (Manríquez et al., 2019George et al., 2020), and identified potential preservation of continuous deposition across the K/Pg boundary (George et al., 2020). This locality has produced a wealth of fossil discoveries that have greatly expanded our understanding of the diversity of vertebrates and plants at southern high latitudes during the end of the Cretaceous (Alarcón-Muñoz et al., 2020;Goin et al., 2020;Trevisan et al., 2020;Martinelli et al., 2021;Soto-Acuña et al., 2021;Suazo Lara and Gomez, 2022), and help elucidate biogeographic patterns during final Gondwanan breakup (reviewed in Reguero and Goin, 2021). While some of these notable discoveries represent partially articulated specimens (i.e., Stegouros elengassen, Soto-Acuña et al., 2021), most vertebrate fossils recovered from the locality are isolated or fragmentary. ...
... SC2, P1, and SC3 are located within floodplain and meandering fluvial deposits, and P2 represents a near-shore marine deposit (Schwartz and Graham, 2005;Manríquez et al., 2019Manríquez et al., , 2021. SC2 is composed of two facies: enantiornithine fossils were recovered from fluvial floodplain facies composed of medium-to coarse-grained sandstones with trough cross-bedding, in proximity to the recently described Stegouros elengasen , and the megaraptoran material was recovered from sandy mudstones with interbedded fine-grained sandstones, near recovered mammal and freshwater turtle remains (Goin et al., 2020;Alarcón-Muñoz et al., 2020;Martinelli et al., 2021). Fossils from P1and SC3 were located in sandy mudstone and fine-grained sandstone facies with carbonaceous material. ...
... The fossils described here from the Río de las Chinas Valley contribute to a larger picture of a thriving vertebrate community at the end of the Cretaceous in the Magallanes-Austral Basin Alarcón-Muñoz et al., 2020;Goin et al., 2020;Martinelli et al., 2021;Soto-Acuña et al., 2021;Aranciaga Rolando et al., 2021;Suazo Lara and Gomez, 2022), and add to the growing record of dinosaurs from Chile. These fossils extend known occurrences of many South American theropod groups farther south, while also providing the southernmost record of Enantiornithines to date and an important new data point of ornithurine birds from the latest Cretaceous. ...
The end Cretaceous mass extinction was marked by a dramatic change in biodiversity, and the extinction of all non-avian dinosaurs. To understand the diversity of dinosaur clades prior to this event, as well as recovery by avian dinosaurs (birds), we need a better understanding of the global fossil record. However, the fossil record from southern localities, particularly southernmost (>60°S) South America, has only recently begun to be described. Discoveries from Patagonia are important to accurately assess global trends in dinosaur diversity, particularly during the latest Cretaceous before the Cretaceous/Paleogene (K/Pg) mass extinction event. Here we describe new theropod dinosaur specimens, representing both associated material and isolated elements, from Upper Cretaceous (Campanian-Maastrichtian) deposits of the Río de las Chinas Valley, Magallanes-Austral Basin, Chile. These discoveries include the southern-most known occurrences of several theropod clades outside of Antarctica, including megaraptorids, unenlagiines, enantiornithines and ornithurines. Notably, these remains provide much needed time-constrained records of smaller theropods, including birds, which are less often recovered from Upper Cretaceous deposits. While fragmentary, these fossils are the first records of theropods from Chilean Patagonia, and provide insight into the distribution of avian and non-avian theropods in southern high latitude ecosystems prior to the K/Pg mass extinction event. Sampling from this region is still sparse, and more fossils from age-controlled sections are needed to accurately assess global extinction dynamics through the end Cretaceous.
... The 'prototribosphenic' molar of 'dryolestoids' marked a critical step in the evolution of the tribosphenic molar, with the appearance of talonid shelf in stem-cladotherians such as 'dryolestoids', which acted as an extending shearing surface and likely assisted in medial movement during occlusion (Grossnickle 2017;Martin et al. 2020). Previous studies have demonstrated considerable phylogenetic uncertainty for 'dryolestoids', which are recovered either paraphyletic (Rougier et al. 2012;Averianov et al. 2013Averianov et al. , 2014O'Meara and Thompson 2014;Wible and Rougier 2017) or monophyletic (Rougier et al. 2011;Chimento et al. 2012;Martinelli et al. 2021). 'Dryolestoids' are the most abundant mammals from the KM site, representing more than 34% of the discovered mammaliaform specimens (Fig. 3). ...
... The triconodont dentition of this amphilestid with three mesiodistally aligned cusps, is probably the plesiomorphic condition for the clade including 'Dryolestoidea' and Theria (Mills 1971;Kielan-Jaworowska and Dashzeveg 1998;Rougier et al. 2007;Averianov and Lopatin 2011). It was preferred to Probainognathus Romer, 1970, which was used as outgroup in the analyses of Rougier et al. (2011Rougier et al. ( , 2012, Chimento et al. (2012), O'Meara andThompson (2014), Wible and Rougier (2017) and Martinelli et al. (2021), because we consider Probainognathus to be too distant from the group of interest, which might cause problems of homology and of character applicability. ...
... The character matrix used in the phylogenetic analyses is mainly based on a compilation of the dental and mandibular characters extracted from the matrices of Rougier et al. (2011) andAverianov et al. (2013), with subsequent modifications by Rougier et al. (2012), Averianov et al. (2014) and Wible and Rougier (2017), to which we added eight new characters. These matrices were also used in other recent works (Chimento et al. 2012;O'Meara and Thompson 2014;Harper et al. 2019;Martinelli et al. 2021). Moreover, they include a large number of 'Dryolestoidea', and especially of Meridiolestida, which are thought to be related to the KM donodontids. ...
The Ksar Metlili Formation, from the Jurassic – Cretaceous transition (Tithonian – Berriasian) of eastern High Atlas Mountains, Morocco, has yielded one of the richest microvertebrate assemblages from the Mesozoic of Gondwana. With at least 19 species, mammaliaforms are particularly diverse. ‘Dryolestoidea’ are the most abundant and the most diverse; nevertheless, only one species, Donodon perscriptoris Sigogneau-Russell, 1991a, of the monotypic Donodontidae, had been described so far. Here, we describe four new species and three new genera of ‘dryolestoids’ from the Ksar Metlili deposits: Donodon minor sp. nov., Stylodens amerrukensis gen. et sp. nov., Anoualestes incidens gen. et sp. nov., and Amazighodon orbis gen. et sp. nov, all of which are included in the Donodontidae based on their dental morphology. We present the first phylogenetic analysis that incorporates the five donodontid species from the Ksar Metlili site into the cladotherian phylogeny. Our new analysis provides evidence for the paraphyly of the ‘Dryolestoidea’: Dryolestidae, ‘Paurodontidae’, Donodontidae, and Zatheria form a clade to the exclusion of the South American Meridiolestida. Donodontids are found to be closer to prototribosphenidans and zatherians than to any other ‘dryolestoid’ family and are more derived than meridiolestidans. This topology refutes a previous hypothesis that meridiolestidans are phylogenetically rooted among donodontids. Our phylogenetic analysis also supports Donodontidae as an endemic African monophyletic group. The close relationships of the donodontids and zatherians suggest that zatherians had a geographical origin possibly from Africa or Gondwana instead of Laurasia.
... As this definition relies on an ontogenetic process (tooth replacement) that is rarely preserved directly, indirect evidence is often employed in identification of the premolar/molar boundary in most taxa. In the absence of teeth preserved in the process of eruption, the most reliable indicator of replacement timing or sequence is wear (Rougier et al. 2003a;Rougier et al. 2007b;Davis 2011;Lopatin and Averianov 2015;Martinelli et al. 2021). The relative accumulation of wear can be used to identify teeth that have been replaced or the sequence in which teeth have erupted (see Luckett 1993). ...
We describe two skull fragments of a new morganucodontan from the Cisco Mammal Quarry (Upper Jurassic Morrison
Formation), preserving portions of the palate and snout in excellent 3D detail as well as the complete upper postcanine
dentition. Morganucodontans are best known by isolated elements and relatively complete skulls of several species of
Morganucodon from the Lower Jurassic of Wales and China; this group is fundamental to our understanding of the
early evolution of mammals. Cifellilestes ciscoensis gen. et sp. nov. possesses derived features of the snout paired with
plesiomorphic construction of the molars; the distal premolars are complex and there is an unusually low count (two) of
strongly imbricated molars. This character combination expands craniodental variation for the group. We sampled mud�stone from the Cisco Mammal Quarry for ash-fall zircon analysis and obtained a date of 151.50 ± 0.28 Ma. This dates the
locality to the earliest Tithonian and slightly younger than other major dated mammal-bearing localities in the Morrison
Formation. Cifellilestes represents one of the youngest members of this group and extends the record of morganucodon�tans in North America by more than 30 Ma. Morganucodontans are a rare component of Late Jurassic faunas but display
surprising dental diversity through variations in a tooth count and cusp morphology of a deeply conserved, generalized
mammalian tooth pattern, which was fully established in brasilodontid (non-mammalian) ancestors at least 80 my prior.
... All mesungulatomorphs are characterized by a reduction in postcanine dental formula, extreme development of bunodonty, and well developed lower molar cingulids. Along with the likely related Reigitherium, Peligrotherium also shows the development of labially extensive exodaenodont lobes on all three lower molar crowns, which are embellished with several neomorphic accessory cuspulids (although see Martinelli et al. 2021 for an alternative interpretation). Most importantly these two taxa have lost all capacity for embrasure shearing (Paéz-Arango 2008), the ancestral mode of oral mechanical digestion in the majority of (presumably insectivorous) Jurassic and Cretaceous cladotherian mammals. ...
The large, bunodont, mammal Peligrotherium tropicalis is an enigmatic member of the earliest Paleocene fauna of Punta
Peligro, Argentina. While being a contemporary of many of the earliest large-bodied “archaic ungulates” in the Northern
Hemisphere, P. tropicalis is a remnant of an endemic Mesozoic non-therian lineage. The interpretation of P. tropicalis as
an omnivore/herbivore has therefore been difficult to evaluate, given its phylogenetic placement outside of the therian
clade, and lack of many of the molar characteristics thought to be essential for the forms of mastication seen in mar�supials and placentals. Here we present a three-dimensional generalization of the classical “bifulcral” biomechanical
model of bite force and joint force estimation, which is capable of accommodating the wide range of mediolateral force
orientations generated by the muscles of mastication, as estimated by the geometry of their rigid attachment surfaces.
Using this analysis, we demonstrate that P. tropicalis is more herbivorously adapted (viz. shows a greater Group 2 relative
to Group 1 jaw adductor advantage for producing postcanine orthal bite forces) than even the hypocarnivorous carniv�orans Procyon lotor and Ursus arctos, and is similar to the ungulates Sus scrofa and Diceros bicornis. This similarity
also extends to the mediolateral distribution of relative muscle group advantage, with Group 1 muscles (responsible
for effecting the initial adduction of the working-side hemimandible into centric occlusion) having greater orthal bite
forces labially; and Group 2 muscles (those responsible for producing occlusal grinding motions) being more powerful
lingually. Finally, we show that P. tropicalis preserves relatively little of its orthal bite force magnitude at high gape,
suggesting that large-object durophagy would not have been a likely feeding strategy.
... The vertebrate paleontological content of the Dorotea Formation includes, frogs, turtles, sauropods, theropods, and ornithischians, birds, and mammals (Soto-Acuña et al., 2014;Manriquez et al., 2019;Alarc on-Muñoz et al., 2020;Goin et al., 2020;Martinelli et al., 2021). This faunistic association is very similar to that present at the Chorrillo Formation Chimento et al., 2020Chimento et al., , 2021Rozadilla et al., 2021, this study). ...
The deposits of the Chorrillo Formation (Maastrichtian) were accumulated during a ‘continental window’ that occurred during the Late Cretaceous in the Austral-Magallanes foreland basin, southern Patagonia, Argentina. The aim of the present contribution is to describe the depositional conditions as well as new vertebrate and plant fossils from this unit. The analysis of these deposits resulted in the definition of five architectural elements: Complex sandy narrow sheets channels (SS), Complex gravelly narrow sheets channels (GS), Sandstone lobes (SL), Thick fine-grained deposits (GF) and Thin dark fine-grained deposits (DF). These were separated into channelized and non-channelized units and represent the accumulation in a fine-grained dominated, fossil rich fluvial depositional system. Vertebrates fossil records include two species of frogs of the genus Calypteocephalella (representing the southernmost record of Pipoidea), snakes belonging to Madtsoiidae and Anilioidea (the latter ones being the first records for the basin), chelid turtles similar to Yaminuechelys-Hydromedusa, meiolaniiform turtles, titanosaur sauropods, megaraptoran theropods, new remains of the elasmarian Isasicursor santacrucensis (including the first cranial remains available for this species), hadrosaur ornithischians, enantiornithine birds. Sharks and elasmosaurs are also recorded and may possibly derive from the overlying marine Calafate Formation. These new taxa, together with previous findings from the Chorrillo Formation, are included into a stratigraphic column, thus providing valuable information that sheds new light on faunistic composition and paleobiogeography of high-latitude biotas of Gondwana.
... After submission and review of this manuscript, Martinelli et al. (2021) described Orretherium tzen, a mesungulatid from the Late Cretaceous of Chile. The specimen consists of a fragmentary left jaw with p2-m3 and an isolated upper molariform identified as the P3. ...
... 7) and not as the sister group to Peligrotherium as proposed by our latest paper describing additional material of Reigitherium (Harper et al. 2018), which we further support here. We agree with Martinelli et al. (2021): "This results from changes in some character-state coding for Reigitherium that differ from the analysis conducted by Harper et al. 2018". Some of those changes are supported by the new material, but others, such as the confirmed presence of upper molar cingula in Reigitherium and cusp proportions, etc., confirms the original scorings. ...
... Some of those changes are supported by the new material, but others, such as the confirmed presence of upper molar cingula in Reigitherium and cusp proportions, etc., confirms the original scorings. Most of the changes introduced by Martinelli et al. (2021) were also modified by us in our current matrix which, by and large, are in agreement. At present, based on our study and the expected impact of Orretherium, we support a sister group relationship for Reigitherium-Peligrotherium. ...
We describe the first maxillae and additional new specimens of Reigitherium bunodontum, a small meridiolestidan from the Late Cretaceous La Colonia Formation, Patagonia, Argentina. The new material supports a dental formula of I?, C1, P4, M3, resolves postcanine positional uncertainty and corrects previous interpretations. Our phylogeny recovers Reigitherium as a meridiolestidan allied to other bunodont Mesungulatoidea, as the sister group of the Paleocene Peligrotherium. Posterior premolars/molars of Reigitherium, and to a smaller degree Peligrotherium, are dominated by an incomplete transverse ridge running between the protoconid-metaconid in the lowers and the paracone-stylocone in the uppers, semi-symmetrical basins developing mesially and distally from these central ridges. The trigonid-derived single transverse crest results from a mesial shift of the robust metaconid, an enhancement of the basin crest stretching from the protoconid/metaconid, and a shallower trigonid basin. The mesungulatoid condition, with its complete absence of talonid, contrasts sharply with that of therians with lophs, or transverse ridges, which involved at least one talonid-derived loph resulting in two transverse crests per tooth. Mesungulatoid meridiolestidans achieved complex tooth-on-tooth occlusion with a predicted increase in herbivory/omnivory, departing from the traditional sharp-cusp insectivores plesiomorphic for meridiolestidans and Mesozoic mammals in general. Reigitherium’s dramatic remodeling of the primitive meridiolestidan molar morphology, extensive continuous occlusal surface, accessory cuspules, and highly textured crenulated enamel illustrates one of most distinctive adaptations to herbivory among Mesozoic mammals.
