identifier	taxonID	type	CVterm	format	language	title	description	additionalInformationURL	UsageTerms	rights	Owner	contributor	creator	bibliographicCitation
836387C5FFCC95738161FA22FACAFA1E.text	836387C5FFCC95738161FA22FACAFA1E.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Rhagomyini Pardiñas & Tinoco & Barbière & Ronez & Cañón & Lessa & Koch & Brito 2022	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> RHAGOMYINI ,  TRIB. NOV.</p>
            <p>(FIGS 2–9, 11)</p>
            <p>Z o o b a n k r e g i s t r a t i o n: u r n: l s i d: z o o b a n k. org:act: BFA3F94-5A18-4AAF-AD22-3A466DDB5005.</p>
            <p> Type genus:  Rhagomys Thomas, 1917 . </p>
            <p> Diagnosis: A tribe of the subfamily  Sigmodontinae , clade Oryzomyalia, grouping small-sized cricetids (head and body length ~ 90 to 100 mm; body mass ~ 20 to 35 g) uniquely diagnosed by the following traits: all digits with deep, transverse grooves; tips of manual digits callused and having a crescent-shaped depression appearing heart-shaped in dorsal view with embedded minute claws; nail (as opposed to a claw) on the hallux; elongated pedal digit V, which reaches the middle of the second phalanx of digit IV; cranium with marked basicranial flexure involving a low emplacement of the mastoid bulla; true fossa occupying the retromolar region developed laterally to m2-m3; completely planed ventral surface to the dentary; pro-odont, smoothly grooved lower incisor showing faintly textured enamel; molars with conspicuous persistently enamelled and conical main cusps connected by thin ridges; anteroconid of m1 composed of a single conulid (as opposed to two conulids) connected to the protoconid and with direct connection between protoconid and hypoconid; tongue unusually long, narrow and cylindrical, lacking both the torus linguae and the sulcus semilunaris (the latter two features presumed in  R. rufescens ); filiform caecum with the external diameter equal to that of the adjacent portion of the colon (after Thomas, 1917; Luna &amp; Patterson, 2003; Percequillo et al., 2004; Luna, 2015; this paper). </p>
            <p> Content: A single genus,  Rhagomys Thomas, 1917: 192 . </p>
            <p> Geographic distribution:  Rhagomyini rodents are distributed extensively in tropical South America in two main cores divided by the Arid Diagonal [see map provided by Moreno Cárdenas et al. (2021: fig. 1) for details]: eastern Andean montane forests, typically above 500 m a.s.l., from southern Ecuador, through Peru to northern Bolivia and in the Atlantic Interior Forest in Brazil. Two isolated records in the Amazonian basin south of the Amazon River in Brazil are also known (Fig. 10). </p>
            <p>Biochron: Recent in Bolivia, Brazil, Ecuador and Peru.</p>
            <p> Other morphological traits: Taxonomic uniqueness promoted a detailed morphological description in  Rhagomys , paradoxically surpassing in this respect most of the other members of the subfamily. Although hampered by the scarcity of available specimens, which produces an inevitable poor control on trait variability, most of the anatomical fields traditionally scrutinized have been reviewed for this rodent (e.g. Luna &amp; Patterson, 2003; Percequillo et al., 2004, 2017; Pinheiro et al., 2004; Abreu-Júnior &amp; Percequillo, 2019). </p>
            <p> From external morphology, almost nothing can be added to the general knowledge of the genus. According to published measurements, the ratio of head and body length to tail length is nearly 1 in adult specimens; rarely does the caudal length exceed the body length by more than 10 mm and in some specimens the latter is slightly longer than the former. Not unexpectedly, some juveniles show markedly longer tails (Medina et al., 2017: table 1), although we suspect that the values reported by Passamani et al. (2011: 829; head and body length = 65 mm, tail length = 105 mm) are incorrect, based on our examination of the published image (Passamani et al., 2011: fig. 6; ratio head and body length to tail length ~0.8). Photographs of live  Rhagomys (e.g. Luna &amp; Patterson, 2003: fig. 2; Medina et al., 2017: fig. 1; Supporting Information, Appendix S3) allow the size of the eyeballs to be judged as conspicuous. No direct data of the eyeball axial length are available for  Rhagomys , hampering any confident quantitative approach. However, based on the detailed picture provided by Medina et al. (2017: fig. 1), we estimated an eyeball axial length of 7.5 mm for the illustrated adult specimen of  R. longilingua (with a body mass of 24 g; Medina et al., 2017: table 1). According to the equation of Howland et al. (2004), the expected eyeball axial length for a mammal of 24 g is 3.72 mm; employing the equation restricted for rodents (Panyutina et al., 2017: 174), this value is 3.75 mm. Both are well below our crude value of 7.5 mm, suggesting that the subjective perception that  Rhagomys has a large eye can be supported quantitatively. To connect this eye size with an improved nocturnal vision seems plausible, but also the possibility of an enhanced ability to visually detect small food items, such as insects, invites further experimental research. The rhinarium in  Rhagomys remains undescribed. Based on two specimens of  R. rufescens and one of  R. septentrionalis it seems similar in western and eastern species (Fig. 9E): furred suprarhinarial region, moderate in size and embellished with two finely sculptured and rounded narial pads (or tubercles; Hill, 1948) positioned below the nostril line. While the dorsal integumental fold appears scarcely developed, the ventral integumental fold has a dominant role in the lateral expression of the rhinarium. Nasal openings, internally flanked by folds (parts of dorsal integumental fold?), are dorsally divided by tegumental promontories that produce rounded internal atrioturbinates. The entire rhinarium is medially dissected by the sulcus medianus, a continuation of the philtrum, which divides well-haired, upper lips (Fig. 9E). Almost nothing was described about the ears in  Rhagomys beyond pilosity and size (e.g. Luna &amp; Patterson, 2003: 5; Percequillo et al., 2004: 242). The specimen MECN 6172 (  R. septentrionalis ) has a rounded auricular pinna, which is concealed basally by head fur and the internal surface of which is covered with delicate hairs. The striking feature of this apparently simple ear is the deep, well recessed concha (Supporting Information, Appendix S12). To our best understanding, this condition could be linked to the internal flexure of the basicranial region and its effect on the several related structures. </p>
            <p> Minor cranial details worthy of comment are the reported absence of an alisphenoid strut and the narrow condition indicated for the zygomatic plate of  R. rufescens (Abreu-Júnior &amp; Percequillo, 2019) . All specimens of this species studied here have a thick alisphenoid strut on both sides of the cranium (Fig.11A), and the same has been reported previously (e.g. Percequillo et al., 2004: 244; Pinheiro et al., 2004: 5); we suspect that the absence highlighted by AbreuJúnior &amp; Percequillo (2019: 77) is an error. In addition, the zygomatic plate in  Rhagomys can hardly be judged as narrow; on the contrary, it is a broad structure (Fig. 11B). However, when examined superficially, it seems narrow because the external shaft is arcuate, giving its posterior border a transverse orientation; in addition, the upper free border shows a marked twist, and the plate is basally broadened (Fig. 11C). As mirrored by several bony structures of the cranium of  Rhagomys , well-developed musculature is probably implied behind this configuration. Even working with damaged material, Thomas (1886: 250) was able to observe a ‘skull with the cranial portion very large’ characterizing  Rhagomys (see also: Luna &amp; Patterson, 2003; Percequillo et al., 2004). The dominance of the braincase is accompanied by a large foramen magnum oriented posteroventrally (Fig. 11D). The latter is better appreciated when viewed from inside, including also the caudal downward orientation of the basioccipital, the middle lacerate foramina present as slits [but not absent, as was stated by Percequillo et al. (2004: 245)] and a long presphenoid (Fig. 3D). Turbinals are comparatively complex (Fig. 3E; cf. Martinez et al., 2018). Interesting to note, although the tegmen tympani abuts, to some degree, a small suspensory process of the squamosal in adults, this condition is not evident in juveniles (Supporting Information, Appendix S13). Special features of the dentary in  Rhagomys include a large mandibular foramen ventrally flanked by an unusually bulging and, in cross-section, rounded crista mandibulae (Supporting Information, Appendix S14). While the former indicates a thick mandibular (trigeminal) nerve, the latter reflects the enlarged development of the incisor. </p>
            <p> Thomas (1917: 193) emphasized the upper incisor features in  Rhagomys indicating ‘… front surface flattened and inclined inwards, so that the resulting relations of the two teeth and the shapes of their tips are about as in the Dormice [  Gliridae ], not as in any of the genera above mentioned [  Oecomys ,  Rhipidomys , etc.]’. Our inspection reinforces the occurrence of this peculiar kind of incisor frontal surface condition and orientation (Fig. 5C), probably associated with a particular feeding strategy (see below). In addition, at least for  R. rufescens , the dentine profile is staggered when the incisor is viewed labially (Fig. 11B). The number of molar roots remains unreported for  Rhagomys . According to the 3D-images, at least  R. septentrionalis has the M1/m1 anchored by four roots, while the M2-M3 are each three-rooted; all lower molars are two-rooted, a widespread condition in sigmodontines (Supporting Information, Appendix S15). Gyldenstolpe (1932: pl. III, fig. 4a) illustrated a four-rooted M1 and a three-rooted M 3 in the holotype of  R. rufescens . </p>
            <p> Although mentioned by Thomas (1886) long ago, the soft palate of  Rhagomys has never been described. In our examination of  R. septentrionalis , the configuration of diastemal and interdental ridges included three and four rugae, respectively. While the former are highly marked and broadened at their midpoints, the latter appear flattened, the first three well directed backwards and leaving an ample medial space (Fig. 9C). The overall morphology of the soft interdental palate appears to facilitate rapid passage of food items more than any action associated with retention or chewing. </p>
            <p> Gross morphology of the stomach is unilocularhemiglandular, first described and illustrated for  R. longilingua (Luna &amp; Patterson, 2003: fig. 11) and subsequently mentioned for  R. rufescens (Pinheiro et al., 2004: 7) . Our examination of single specimens each of  R. rufescens and of  R. septentrionalis confirms this generic pattern, which includes a heart-outlined organ with roughly subequal, cornified and glandular epithelia, a bordering fold not protruding to the left of the oesophageal opening (but directed posteriorly toward the greater curvature), a shallow incisura angularis and a scarcely differentiated prepyloric part (Fig. 9D; Supporting Information, Appendix S16). Finally, the gall bladder was reported as absent in  R. longilingua (Luna &amp; Patterson, 2003: 12) , and the same condition can be asserted for the other species of the genus based on the specimens we dissected (  R. rufescens, MZUFV-CM 3706;  R. septentrionalis, MECN 6172). </p>
            <p>Nomenclatural remarks</p>
            <p> The genus name is probably derived from Ancient Greek ῥαγόω = rhagóō, literally to crack (Supporting Information, Appendix S17) and µυς, mouse. Although not mentioned by Thomas (1917), this name possibly refers to the fact that the soles of the hind and forefeet are dissected by pronounced transverse grooves. The name of the tribe is derived from the addition of the tribal ending -ini, therefore,  Rhagomyini . </p>
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	https://treatment.plazi.org/id/836387C5FFCC95738161FA22FACAFA1E	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Pardiñas, Ulyses F. J.;Tinoco, Nicolás;Barbière, Franck;Ronez, Christophe;Cañón, Carola;Lessa, Gisele;Koch, Claudia;Brito, Jorge	Pardiñas, Ulyses F. J., Tinoco, Nicolás, Barbière, Franck, Ronez, Christophe, Cañón, Carola, Lessa, Gisele, Koch, Claudia, Brito, Jorge (2022): Morphological disparity in a hyperdiverse mammal clade: a new morphotype and tribe of Neotropical cricetids. Zoological Journal of the Linnean Society 196: 1013-1038, DOI: 10.1093/zoolinnean/zlac016, URL: https://doi.org/10.1093/zoolinnean/zlac016
836387C5FFC8956F837BF9B3FACCFCC2.text	836387C5FFC8956F837BF9B3FACCFCC2.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Rhagomys Thomas 1917	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> RHAGOMYS : GENERIC CONTENT AND UNIQUENESS </p>
            <p> Ample evidence suggests that  Rhagomys , as currently understood (i.e. composed of three species; see: Moreno Cárdenas et al., 2021), represents two generic entities. The point is controversial because it relies on epistemological aspects, in particular what degree of morphological/genetical distance can be allocated to a genus before its value is diluted [see a discussion of this issue applied to  Oryzomyini rodents in Weksler (2006)]. Differences between  R. rufescens and (  R. longilingua +  R. septentrionalis ) include trenchant morphological (e.g. absence vs. presence of spiny fur, presence vs. absence of the anterolingual conule of the M1), genetical (&gt; 17% in Cytb distance between species pairs, a value well above the median recorded for the order  Rodentia ; see: Schrago &amp; Mello, 2020) and geographical (Atlantic Interior Forest vs. eastern Andean forest and contiguous Amazonian lowlands) contrasts. We suggest that western  Rhagomys populations, from northern Bolivia (Villalpando et al., 2006) to south-eastern Ecuador (this paper), including two different species, deserve a new generic assignment. A similar case is exemplified by the erection of the murine  Musseromys Heaney et al., 2009 despite its clear morphological and genetical closeness to  Carpomys Thomas, 1895 . Heaney et al. (2009: 215) were adamant, indicating that ‘although our molecular data strongly suggest that  Carpomys is the closest relative of the Banahaw mouse [i.e.  Musseromys ], on the basis of these 16 characters, we reject the option of considering them to be members of a single genus’. Most of these 16 characters, if not all, can be judged as subtle differences (e.g. lower incisors more slender, coronoid process of the mandible shorter and more sharply pointed) in the context of those separating western vs. eastern species in  Rhagomys . It is vox populi that  R. longilingua was originally stated as a type species of a new genus, but because of subsequent work was finally placed in  Rhagomys . We hope that the morphological scrutiny developed in the present contribution triggers a reappraisal of that pending taxonomic issue. </p>
            <p> Uncertainties about  Rhagomys relationships have been largely due to the poor quality and scarcity of the available material. Although the type species was described by the end of the 19 th century (Thomas, 1886), the basis for the recognition of the genus was a second animal acquired decades later (Thomas, 1917). As has been reviewed in detail by previous authors (Luna &amp; Patterson, 2003: 13–17; Percequillo et al., 2004: 253), the acute perception of O. Thomas pointed to connect  Rhagomys with oryzomyines and thomasomyines. This author was mostly guided by external morphology because not only the cranium of the holotype is badly preserved (e.g. Gyldenstolpe, 1932: pl. III, fig. 4), but also skin features were highlighted in successive diagnoses (Thomas, 1886, 1917). In any case, Thomas (1917: 193) was unusually expressive, pointing to the uniqueness of the genus as reflected in its molars: ‘The teeth are therefore almost as in certain Phyllostomid bats, with smooth glossy surface and simple conical cusps, which are evenly spaced- slightly slanted backwards, 6, 4, and 2 in number on the three teeth. Below the teeth are similarly modified, the cusps slanting forwards.’ He added, ‘Still younger specimens of  Rhagomys will be welcome to show what trace of the normal foldings and ridges is exhibited by the molars when absolutely unworn; but it is evident there cannot be much.’ </p>
            <p> Luna &amp; Patterson (2003: 19) hypothesized that the unique morphology represented by the incisors of  R. longilingua is related to a singular feeding activity: the collection of invertebrates boring bamboo canes. We elaborate on this proposal here: the entire morphotype of  Rhagomys can be understood as a specialization for living and exploiting dense understory habitats consisting mostly of reeds, bamboos and several similar plants (e.g.  Gynerium Willd. ex P.Beauv. ,  Poaceae ). Bamboos cover extensive areas in South America (&gt; 100 000 km 2), including a diversity of about 20 genera and 430 species (Judziewicz et al., 1999). Even discarding Patagonian records that traced the history of these unique grasses to the Eocene, it is easy to envision the abundance of this kind of vegetation on the continent at least since the Pliocene (Wilf, 2020). The assumption that a sigmodontine specializes in exploiting bamboo directly or indirectly as a resource is not far-fetched because other rodents have also followed this path (e.g. murids in Asia such as  Hapalomys Blyth, 1859 or  Kadarsanomys Musser, 1981 ; see: Bartels, 1937; Musser, 1972). Field observations of  R. septentrionalis suggest that this animal lives in dense riverine understory, which consists mainly of bamboos and  Gynerium , and the latter is used to construct spherical nests about 1 or 2 m high (Supporting Information, Appendix S18). Collection data for  R. longilingua also support a close association with bamboos (Luna &amp; Patterson, 2003), and the same was found for several of the trapping sites in the case of  R. rufescens (e.g. Steiner-Souza et al., 2008). </p>
            <p>ARBOREAL SIGMODONTINES: TWO STRATEGIES</p>
            <p> It is a biological commonplace that different strategies, reflected in differential phenotypes, allow organisms to face similar challenges (e.g. McGhee, 2011). Focusing on sigmodontine rodents, this axiom was masterfully addressed by Hershkovitz (1966: 95) regarding fossoriality, when he wrote: ‘Fossorial cricetines, like fossorial rodents in general, are of two functional types. The first is shrew- or mole-like superficially but with weak teeth and jaws and is primarily insect and worm eating. The second is pocket gopher-like with strong teeth and jaws and is primarily grass, forb and root eating.  Kunsia Lichtenstein, 1830 is the outstanding, if not the only living gopher-like cricetine. Soricine or talpine cricetines are represented by neotropical oxymycterines and many akodonts, most notably the monotypic  Blarinomys Thomas, 1896 . They are characterized by thick, soft pelage, weak zygomata and mandible. They are generally small and wiry. Gopher-like rodents are comparatively large and stocky and nearly all their specialized characters … contrast with those of the soricine type.’ </p>
            <p> To date, arboreal-scansorial sigmodontine rodents have been viewed as a single morphotype characterized by a combination of external traits, including ‘… long semi-prehensile tails covered, at least terminally, with long tactile hairs … feet are broad, with long and partially opposable outer digits, recurved claws, and enlarged plantar tubercles adapted for clutching slender branches and twigs. The short muzzle and enlarged eyes of these arboreal mice afford a wide field of frontal vision’ (Hershkovitz, 1969: 42). Members of several tribes, especially oryzomyines and thomasomyines, but also euneomyines (  Irenomys Thomas, 1919 ), wiedomyines (e.g.  Juliomys González, 2000 ), etc., display this suite of features (e.g. Pearson, 1983; Tribe, 1996; Rivas &amp; Linares, 2006). </p>
            <p> Here we assume that  Rhagomyini represent a second arboreal morphotype that evolved to face the exploitation of the vertical dimension in dense understory, which is mostly dominated by woody plants characterized by moderately thin branches crossing in all directions. To deal with such a habitat, external specializations are likely to be different from those traditionally observed in arboreal sigmodontines (Hershkovitz, 1969). In this context, manual grasping would be enhanced by a larger system of pads, calluses and grooves, and a shortening of the claws on both manus and pes. Contrary, perhaps, to expectations, the tail has lost its traditional role in balancing (Cartmill, 1985) through a reduction in length and apical hairiness (Fig. 12). </p>
            <p> The  Rhagomyini morphotype seems to favour not solely climbing activities but also a particular trophic behaviour associated with an arboreal mode of life: insectivory. The stomach contents of  R. longilingua included insects, and the powerful musculature of this mouse has been associated with the ability for cane boring (Luna &amp; Patterson, 2003: 19). The exclusive incisor features shown by  Rhagomys , especially the fine groove and the cutting-edge indentation of the lower incisor, point in the same direction. Functionally, incisor longitudinal striae have been associated with strengthening the tooth while improving retraction when gnawing woody material (Russell, 1968; Akersten, 1973). Both are desirable qualities for a rodent determined to pierce the hard exterior of cane, presumably to extract boring invertebrates. In this context, manus morphology deserves special attention; they are so impressive when the animal is alive that the suspicion that some other role beyond climbing is involved seems certain (Supporting Information, Appendix S3). Cartmill (1974: 69) emphasized: ‘Forestfloor predators may climb to nose out insects concealed in the dense crowns of palms and similar plants … but their search procedures are poorly adapted to stalking insects amid the slender branches of the canopy and shrub layers. The insects which abound in these strata are attacked by small predators … which locate and track prey with their eyes and seize it with their hands ….’ We believe that the combination of insectivory and arboreality triggered the unique suite of specializations observed in  Rhagomyini , which include not only cheiridia or tail features, but also large eyes, a short snout, etc. This morphofunctional pathway is uniquely present in these rodents within the sigmodontine universe; in contrast, all other known arboreal members of the subfamily have focused on the consumption of vegetal items (Pardiñas et al., 2017). </p>
            <p>FACING MORPHOLOGICAL DISPARITY IN SIGMODONTINES</p>
            <p> Morphological disparity underpins the entire sigmodontine radiation and clearly constitutes one of the biggest challenges to understanding its evolutionary history, and encapsulating that history in a classificatory scheme. The last two decades have centred on three strategies to deal, at the classificatory level, with this issue: (1) expand already-named tribes to accommodate morphologically divergent taxa (e.g. Smith &amp; Patton, 1999; D’Elía et al., 2006; Gonçalves et al., 2020); (2) erect new tribes to accommodate these taxa (e.g. Pardiñas et al., 2015; Salazar Bravo et al., 2016); or (3) retain these taxa as ‘unique lineages’ (  Sigmodontinae incertae sedis) while awaiting future data (e.g. Voss, 1993; Ventura et al., 2013). Strategies 1 and 2 are permeated by the same basic question: what degree of morphological disparity is acceptable before tribal unity (= diagnosability) is broken? When Smith &amp; Patton (1999) decided to expand  Akodontini to include Scapteromyini, the nature of the evidence employed (cytochrome b) meant that the above-mentioned question was not addressed. On the contrary, in the recent proposed expansion of the Wiedomyini to include two sylvan enigmatic genera,  Juliomys and  Phaenomys Thomas, 1917 (see: Gonçalves et al., 2020), morphological evidence was barely discussed. As such, the resulting new concept of Wiedomyini implies a high degree of variability reflected in the main anatomical systems analysed and the same is true for the current  Akodontini . When D’Elía et al. (2006: 562) assigned  Rhagomys to  Thomasomyini , they did mention morphological differences highlighted by Pacheco (2003), but chose to base their final decision on the shared molecular characters. </p>
            <p> Voss (1993: 25) was adamant about how to deal with these ‘refractory’ unique genera: ‘  Delomys is one of many pentalophodont genera that cannot be assigned to any demonstrably monophyletic taxon less inclusive than the Neotropical muroid ingroup identified earlier …. Placing these taxa in a formally named tribe, such as the  Thomasomyini … would be a mistake because, inevitably, all coordinate taxa are treated equivalently by nonsystematists. Equally useless is the option of erecting a monotypic tribe for each genus judged to have achieved some arbitrary degree of difference.’ However, knowledge accumulated over the last three decades since Voss’s publication, particularly with the advent of molecular data, has produced a refreshed impetus to face these questions. Contrary to the opinion, popularized by several taxonomists, that people simply name clades because they like to name organisms (vox populi), recognition by naming distinctive tribes has intrinsic value. The case of the sigmodontine  Reithrodon Waterhouse, 1837 exemplifies this point. This rat was early assigned to a ‘sigmodont’ group (Hershkovitz, 1955), but shortly thereafter was recognized as a separate tribe (Vorontsov, 1959, 1967, 1982). Several morphologically based contributions cemented its assignment to  Phyllotini (e.g. Olds &amp; Anderson, 1989; Braun, 1993; Steppan, 1995), but when molecular data retrieved  Reithrodon as a separate branch of the sigmodontine radiation (e.g. Smith &amp; Patton, 1999; Jansa &amp; Weksler, 2004), Reithrodontini were rapidly resurrected (Musser &amp; Carleton, 2005; Cazzaniga et al., 2019). However, if Vorontsov (1959) had not created the tribe, certainly  Reithrodon would be a ‘unique lineage’ by now. Nothing impedes a classification composed of tribes and isolated genera, since the latter can (at least potentially) be understood as unnamed monotypic tribes. However, when the history of a clade is added to the equation, the option to maintain numerous morphologically divergent genera seems a poor strategy. Revisionary studies on fossils originally envisioned as  Phyllotini , such as  Auliscomys osvaldoreigi Quintana, 2002 and  Olympicomys vossi Steppan &amp; Pardiñas, 1998 (Barbière, 2019; Barbière et al., 2021b), support placement of both taxa in Reithrodontini (see also: Barbière et al., 2016). In this new enlarged context, and monotypic in its recent expression, the tribe acquires a new dimension to analyse the structure of the entire radiation. </p>
            <p> The case we address herein, a disparate morphology (  Rhagomys ) subsumed into a recognized tribe (  Thomasomyini ) by molecular linkage, is not an exception: the taxonomic history of sigmodontines offers numerous other examples. Most of these have been recognized by previous studies (e.g. Gonçalves et al., 2020), including relationships resolved as sisters between  Delomys and  Phyllotini (a result repeatedly reported since Jansa &amp; Weksler, 2004) or  Abrawayaomys and  Akodontini (e.g. Ventura et al., 2013). These seem to be iconic examples of pairs where the degree of morphological disparity is so great that no attempt is made to expand the tribes to resolve these relationships. In other words, returning to the case of  Delomys commented on above, it was never proposed to be included in  Phyllotini . Including  Delomys within  Phyllotini would be destructive, as it would eliminate an otherwise morphological cohesion. This suggestion is an eloquent indication that molecular-based associations have a limit, and that limit, beyond the fact that we may not like to recognize it, is arbitrary. </p>
            <p> There are many other overlooked examples of morphological disparity throughout the sigmodontines, and we are persuaded that these must be carefully reviewed if we are to obtain a complete understanding of the radiation. Examples of neglected cases include, among others, the phylogenetic association of  Scolomys Anthony, 1924 and  Zygodontomys J.A. Allen, 1897 with the remainder of the oryzomyines (e.g. Weksler, 2003, 2006; Pine et al., 2012; Percequillo et al., 2021). Both genera are so distinct in many aspects of their morphology (Voss, 1991; Patton &amp; da Silva, 1995), that they probably each deserve a monotypic tribe. This does not imply that one should ignore their basal relationship with the oryzomyines, as the same is valid between  Rhagomyini and  Thomasomyini . </p>
            <p> Nevertheless, the most challenging situation is our current understanding of the main dichotomy embraced by the subfamily: Oryzomyalia vs. Sigmodontalia. This binary scheme, revealed and propagated by seminal genetic studies (e.g. Engel et al., 1998; Casavant et al., 2000; Steppan et al., 2004; Leite et al., 2014), hides a paramount case of morphological disparity: the sister-relationship between the two components of Sigmodontalia. They are the residue of the classical ‘sigmodont’ group of Hershkovitz (1955), limited to  Sigmodon Say &amp; Ord, 1825 as the only living element of  Sigmodontini and the members of  Ichthyomyini . It is difficult to imagine a more trenchant morphological distance than that involved in this tribal dichotomy. It can be argued that  Sigmodon represents a conservative, grazing sigmodontine (Voss, 1992), while ichthyomyines are a hyperspecialized tribe focused on freshwater carnivory (Voss, 1988), but this does not necessarily explain why they are separated by a morphological gap of such magnitude. To suppose that ‘something’ (one or more genera or tribes) is missing from this evolutionary puzzle (more probably extinct than awaiting discovery) emerges as a crucial necessity. Because  Sigmodon is widespread in North America and easy to catch and breed, it has been intensively studied and emerges as the emblematic sigmodontine capable of biologically representing the entire subfamily (e.g. Rinker, 1954; Hershkovitz, 1962; Martin, 1979; Peppers et al., 2002). However, to focus only on the molar pattern of this genus resists any simplistic approach and results in a rara avis (Barbière et al., 2019). </p>
            <p> According to the most recent phylogenetic reconstruction, intendedasthe‘backbone’ofsigmodontine radiation (Parada et al., 2021),  Sigmodontini and  Ichthyomyini have a long history as separate branches, with an estimated split prior to the estimated time of diversification of the Oryzomyalia (see also: Steppan et al., 2004; Schenk et al., 2013). As a first step toward improving this molecular ‘backbone’, we propose to change our current understanding of sigmodontine radiation to a ternary scheme. In this new scenario,  Sigmodontini ,  Ichthyomyini and Oryzomyalia are comparable evolutionary units, each encompassing a long and idiosyncratic history of diversification (represented by fossil and living records). While subtle, this proposal is crucial because it enriches our understanding of the full complement of diversity within the clade. That morphological disparity should be treated with the same emphasis that is currently given to molecular evidence is the substantive theme of our contribution. </p>
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	https://treatment.plazi.org/id/836387C5FFC8956F837BF9B3FACCFCC2	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Pardiñas, Ulyses F. J.;Tinoco, Nicolás;Barbière, Franck;Ronez, Christophe;Cañón, Carola;Lessa, Gisele;Koch, Claudia;Brito, Jorge	Pardiñas, Ulyses F. J., Tinoco, Nicolás, Barbière, Franck, Ronez, Christophe, Cañón, Carola, Lessa, Gisele, Koch, Claudia, Brito, Jorge (2022): Morphological disparity in a hyperdiverse mammal clade: a new morphotype and tribe of Neotropical cricetids. Zoological Journal of the Linnean Society 196: 1013-1038, DOI: 10.1093/zoolinnean/zlac016, URL: https://doi.org/10.1093/zoolinnean/zlac016
