Figure 6 - uploaded by Nathan S. Upham
Content may be subject to copyright.
![The timing of 1. divergence events throughout the molecular timetree of Ctenohystrica (grouped in 1 Ma bins from the species-level timetree [not shown]) in relation to 2. contemporaneous climatic and geologic events. Note that only the surviving lineages are represented in the timetree. The oxygen isotopic curve is modified from Zachos et al. (2008) and is used to represent global climatic changes. The temperature scale assumes an ice-free ocean, so only applies directly to the period prior to ~35 Ma (Eocene–Oligocene boundary), after which a global cooling event initiated ice sheets in Antarctica and a shift to an " icehouse " world (Livermore et al., 2004; Lagabrielle et al., 2009; Goin et al., 2012). Other references for geoclimatic events are as follows: the GAAR (Great Antilles/Aves Ridge) land connection ~34 Ma for dispersal to the Caribbean from South America (Iturralde Vinent and MacPhee, 1999); global drop in sea levels ~11 Ma (Haq et al., 1987); orogenic episodes and percentages of modern elevations in the Central Andes 22-20 Ma and 12-10 Ma, and Northern Andes 5-2 Ma (Gregory– Wodzicki, 2000; Lomize, 2008); Altiplano-Puna rainshadow by 15 Ma (Hartley, 2003); Pebas wetlands in Amazonia 23-11 Ma and terra firma forests beginning ~7 Ma (Hoorn et al., 2010; Latrubesse et al., 2010; Shephard et al., 2010); establishment of the east flowing Amazon River between 10.6 and 9.7 Ma (Figueiredo et al., 2010); and stages of decreasing forest cover in Patagonia (Barreda and Palazzesi, 2007; Barreda et al., 2010). The timing of geological epochs is from Gradstein et al. (2004).](profile/Nathan-Upham/publication/282577627/figure/fig6/AS:421181967618051@1477429014862/The-timing-of-1-divergence-events-throughout-the-molecular-timetree-of-Ctenohystrica.png)
The timing of 1. divergence events throughout the molecular timetree of Ctenohystrica (grouped in 1 Ma bins from the species-level timetree [not shown]) in relation to 2. contemporaneous climatic and geologic events. Note that only the surviving lineages are represented in the timetree. The oxygen isotopic curve is modified from Zachos et al. (2008) and is used to represent global climatic changes. The temperature scale assumes an ice-free ocean, so only applies directly to the period prior to ~35 Ma (Eocene–Oligocene boundary), after which a global cooling event initiated ice sheets in Antarctica and a shift to an " icehouse " world (Livermore et al., 2004; Lagabrielle et al., 2009; Goin et al., 2012). Other references for geoclimatic events are as follows: the GAAR (Great Antilles/Aves Ridge) land connection ~34 Ma for dispersal to the Caribbean from South America (Iturralde Vinent and MacPhee, 1999); global drop in sea levels ~11 Ma (Haq et al., 1987); orogenic episodes and percentages of modern elevations in the Central Andes 22-20 Ma and 12-10 Ma, and Northern Andes 5-2 Ma (Gregory– Wodzicki, 2000; Lomize, 2008); Altiplano-Puna rainshadow by 15 Ma (Hartley, 2003); Pebas wetlands in Amazonia 23-11 Ma and terra firma forests beginning ~7 Ma (Hoorn et al., 2010; Latrubesse et al., 2010; Shephard et al., 2010); establishment of the east flowing Amazon River between 10.6 and 9.7 Ma (Figueiredo et al., 2010); and stages of decreasing forest cover in Patagonia (Barreda and Palazzesi, 2007; Barreda et al., 2010). The timing of geological epochs is from Gradstein et al. (2004).
Source publication
The Caviomorpha is a diverse lineage of hystricognath rodents endemic to the Americas and Caribbean islands. We analyzed evolutionary relationships within 11 families of caviomorphs and their relatives in the suborder Ctenohystrica using a supermatrix of 199 taxa and DNA sequences from five genes. New gene sequences were generated for 33 genera, in...
Contexts in source publication
Context 1
... Climatic Optimum (MECO -see Fig. 5; Zachos et al., 2008), which occurred at ~41.5 Ma ( Bohaty and Zachos, 2003). Given that the MECO event occurred shortly before the oldest known South American caviomorph fossils ~41 Ma and shortly after their inferred split from African phiomorphs, these biotic and abiotic events are coincidentally linked (Fig. 6). However, evidence that the MECO event initiated this biotic dispersal across the Atlantic Ocean is purely circumstantial, and unlikely to be corroborated because waif dispersals are by definition rare and idiosyncratic (e.g., via rafts of floating debris; Lavocat, 1969;Martin, 1994a;Houle, 1998). Nevertheless, the scenario of ...
Context 2
... mid-Miocene (17.4 Ma) split between Capromyidae and a lineage of Brazilian echimyids considerably postdates GAAR (Greater Antilles + Aves Ridge; Fig. 6.2), a transitory corridor for dispersal from northern South America to the Caribbean ~34 Ma (Iturralde-Vinent and MacPhee, 1999).The delayed 9.8 Ma age for crown Capromyidae supports the idea that a considerable portion of this radiation is now extinct (Woods et al., 2001;Borroto-Páez and Mancina, 2011). The oldest capromyid fossil, ...
Context 3
... and paleoclimatic studies allow us to glimpse the varied and dynamic envi- ronments that caviomorph ancestors would have experienced during their Middle Eocene-Re- cent evolutionary history (Fig. 6). Caviomorph ancestors inhabited a hot and wet "greenhouse" world that lacked polar icecaps and had mean global temperatures >10 °C warmer than they are today (Zachos et al., 2008;Goin et al., 2012). A dramatic global cooling event unfolded near the Eocene-Oligocene boundary that is linked to the opening of the Drake Passage between ...
Context 4
... most dramatically for caviomorph rodents was the major differentiation of South American habitats into arid southern and mesic northern biomes after ~18 Ma. Substantial global cooling following the Mid-Miocene Climatic Optimum, along with the initiation of a rainshadow in most of the Southern Cone ( Fig. 6.2), transformed the continent into multiple distinctive biomes, each with unique environmental challenges to resident caviomorphs (Croft et al., 2009;Flynn et al., 2012). The fossil record of Octodontoidea appears to especially reflect these changes, with the mesic-adapted clade of Echimyidae-Capromyidae represented in Pata- gonian ...
Context 5
... of these clades: What factors led to the greater longevity of lineages in Echimyidae-Capromyidae (many Miocene-aged lineages) compared to those in Octodontidae-Ctenomyidae (two surviving lineages from the late Miocene)? The fact that the southern clade of octodontids and ctenomyids had to adapt to arid climates unprec- edented in the Paleogene (Fig. 6.2), suggests one reason for the apparently greater turnover of species during the initial stages of their radiation ( Fig. 5; Upham, 2014). Spatiotemporal and ecomorphological data from the fossil record need to be reconciled with the region's progressive aridification, especially now that rates and sequences of lineage diversification ...
Context 6
... juxtaposition of caviomorph diversification events (Fig. 6.1) along with the climatic and environmental factors that might have shaped their evolutionary history ( Fig. 6.2) is intended only to be heuristic; we emphasize it is not exhaustive. In another study, we examine the tempo and mode of caviomorph diversification and disparification more directly. However, Figure 6 offers a glimpse of the major environmental factors that would have shaped caviomorph evolution from the Oligocene-Miocene, prior to the ...
Context 7
... another study, we examine the tempo and mode of caviomorph diversification and disparification more directly. However, Figure 6 offers a glimpse of the major environmental factors that would have shaped caviomorph evolution from the Oligocene-Miocene, prior to the arrival of other rodent groups (including squirrels, beavers, and gophers) and placental lineages to South American ecosystems (Simpson, 1980). The opportunities that caviomorphs encountered and were able to exploit are directly reflected in their diversity and disparity, but we are still far from understanding this complementarity. ...
Citations
... Popularly known as tuco-tucos, these rodents are distributed in the austral cone of South America, from Perú and Brazil to Tierra del Fuego, Argentina (D'Elía et al., 2021). The origin of the genus has been estimated to be from 10 to 3 Ma, depending on the study (Parada et al., 2011;Upham & Patterson, 2015;Santi et al., 2021), but there is agreement in that extensive and rapid cladogenesis took place around 3-1 Ma with the development of eight different species groups (Parada et al., 2011;Santi et al., 2021) and more than 60 extant species, constituting one of the most species-rich genera among mammals (D'Elía et al., 2021). ...
Satellite dna s (satDNA) have long been recognized as a major driving force in karyotypic repatterning, owing to their ability to recombine between non-homologous chromosomes. A quite extensively studied model is the Repetitive PvuII Ctenomys Sequence (rpcs), the main component of constitutive heterochromatin in rodents of the genus Ctenomys (Rodentia, Ctenomyidae). At the genus level, fluctuations in rpcs copy number have been previously associated with karyotypic instability. However, when a microevolutionary approach was assayed in the most karyotypically variable lineage of the genus, the vast population-level copy number variation precluded any possibility of analyzing it in a phylogenetic framework. The existence of sex-related differences as a source of variability was not considered until later, when chromosomal banding suggested that the Y chromosome may be a significant reservoir of rpcs. This study aimed to investigate the bias associated with the presence of the Y chromosome in rpcs copy number variation in the Corrientes group of Ctenomys. The results revealed that the Y chromosome harbors almost twice the amount of rpcs compared to the rest of the chromosome complement, explaining the high levels of intrapopulation variation. The evolution of rpcs copy number in males and females showed independent patterns, attributable to the presence/absence of the Y chromosome. The correlation between rpcs dynamics and diploid number fluctuations was also investigated, concluding that some karyotypic repatterning events could be explained by satDNA amplification/deletion, but not all of them. This study highlights the importance of considering differences resulting from the differential accumulation of satDNA in the heterogametic chromosome.
... For example, hutias have been traditionally considered as a separate family (i.e., Capromyidae), closely related but not part of monophyletic Echimyidae (e.g., Woods and Howland 1979;Verzi et al. 2014). Molecular data have conclusively shown that hutias are nested within Echimyidae (Fabre et al. 2014(Fabre et al. , 2017Upham and Patterson 2015) and warrant no more than subfamily recognition (i.e., Capromyinae; Courcelle et al. 2019). On the other hand, in the absence of biomolecular evidence, the relationship of several extinct mammals continues to be problematic because several of them have not been included in phylogenetic analyses and their morphology is highly derived. ...
... Along with other indicators, observations like these suggest that caviomorph inner ear structures may contain a strong phylogenetic signal. To test this proposition, we analyzed here inner ear features across an extensive taxon sample, utilizing a molecular backbone approach (Upham and Patterson 2015;Upham et al. 2019) and comparative phylogenetic methods (Blomberg et al. 2003) as a basis for identifying potentially informative characters. We also used geometric morphometrics to explore interspecific variation in inner ear features in extant caviomorph rodents. ...
... If this hypothesis is correct (but see Marivaux et al. 2022), the antiquity of this radiation must go back to the late Paleogene, as Borikenomys, recently discovered in the early Oligocene of Puerto Rico displays potential affinity with heptaxodontids, all of which share a similar enamel microstructure pattern not documented in any echimyids or capromyines that is unlikely to be due to homoplasy (Marivaux et al. 2020). One consequence of the phylogenetic argument of Woods et al. (2021) is that placing the split between Capromyinae and South American Echimyidae in the Early Miocene is either far too young and at least inconsistent with a single colonization event (e.g., Upham and Patterson 2015;Fabre et al. 2017;Courcelle et al. 2019;Woods et al. 2021), or, alternatively, that the early colonization of Puerto Rico by the ancestor of the Borikenomys lineage was quickly followed by its extinction. This alternative is somewhat difficult to envisage if we consider the hypothesis of a phylogenetic link of this taxon with the Heptaxodontidae (Amblyrhiza, Elasmodontomys, Quemisia, etc., sensu Marivaux et al. 2020Marivaux et al. , 2022. ...
With their past and current diversities, West Indian caviomorph rodents dominate the terrestrial mammalian fauna of the Caribbean archipelago. Many of these species have recently become extinct, including the emblematic giant forms known as Heptaxodontidae. The higher-level systematics and content of this family have been widely disputed over the last decades (i.e., membership in Cavioidea vs. Chinchilloidea vs. Octodontoidea). Here we analyzed the phylogenetic signal provided by several characters of the caviomorph inner ear to adress the phylogenetic affinities of the West Indian heptaxodontids. For this, we assembled an exhaustive taxonomic sampling (N = 100) of extant North and South American caviomorphs (including representatives of all families) and a wide array of West Indian forms among octodontoid echimyids (extant and extinct capromyines, as well as extinct heteropsomyines), and some heptaxodontid subfossil taxa such as Amblyrhiza, Clidomys, and Elasmodontomys. Geometric morphometrics and comparative phylogenetic methods were employed to explore shape differences of the inner ear and their potential systematic implications. Our results show that: (1) allometry is a major contributor to shape variation in the bony labyrinth; (2) shape variation bears a strong phylogenetic signal, providing diagnostic characters for Caviidae and Erethizontoidea; and (3) Amblyrhiza and Clidomys are morphologically closer to Chinchilloidea with which they have potential phylogenetic affinities. Elasmodontomys remains a problematic taxon as it exhibits inner ear features that are consistent with either Chinchilloidea or Octodontoidea, depending on how the allometric component is evaluated.
... These curious mammals have evolved on this continent probably since the Middle Eocene (Antoine et al., 2012; but see Campbell et al., 2021), and today they represent a significant part of the local endemic diversity of mammals, with almost 250 species . The high diversification of these rodents, associated with ecomorphological adaptations, promoted the colonization of most environments likely inhabited in Editorial handling: Analía M. Forasiepi *Correspondence: Leonardo Kerber leonardokerber@gmail.com Full list of author information is available at the end of the article this land mass Upham & Patterson, 2015). ...
... The diversity of extant and extinct crown Caviomorpha is included in four major clades: Erethizontoidea, Cavioidea, Chinchilloidea, and Octodontoidea (D'Elia et al., 2019;Fabre et al., 2015;Upham & Patterson, 2015). Fossils of caviomorphs indicate that these groups were already split during the Paleogene. ...
Here I reviewed the Pleistocene caviomorphs collected by Santiago Roth (collection from Catalog No. 5) and housed at the paleontological collection of the Paläontologisches Institut und Museum, Universität Zürich, Zurich (Switzerland). The fossils were found in Pleistocene strata from Buenos Aires and Santa Fé provinces (Argentina) during the late nineteenth century. The material includes craniomandibular remains assigned to Lagostomus maximus (Chinchilloidea: Chinchillidae), craniomandibular and postcranial (thoracic and sacral vertebra, left scapula, left femur, and right tibia) bones identified as Dolichotis sp. (Cavioidea: Caviidae), and a fragmented hemimandible and isolated tooth of Myocastor sp. (Octodontoidea: Echimyidae). Other rodent specimens from this collection ( Ctenomys sp. and Cavia sp.) are possibly sub-recent materials.
... The topology of the maximum clade credibility (MCC) tree obtained from BEAST reflects the known higher taxonomic groupings of the Rodentia taxa used, as compared to other reports (Fig. 4;Upham and Patterson 2015;Swanson et al. 2019). It is worth noting that several contradicting phylogenetic topologies for the Hystricomorpha families have been reported in the past, which for one could be an artefact of the molecular marker used (Huchon et al. 2000;Honeycutt et al. 2007;Heritage et al. 2016;Swanson et al. 2019). ...
... The accuracy of the estimated Thyronomys divergence dates were assessed by comparing estimates of well-known taxa to the literature. The MRCA date estimated for Phiomorpha in this study is slightly younger than estimates reported by Upham and Patterson (2015), although these estimates do overlap with the confidence intervals calculated in that study. The Phiomorpha date calculated in the current study further overlaps with the confidence intervals of estimates from Sallam et al. (2009), Upham and Patterson (2012) and Huchon et al. (2007). ...
... This date estimate is relatively younger than what has been reported by others (8.6-13.6 Mya; Sobrero et al. 2014;Upham and Patterson 2015;Kumar et al. 2017). These lower divergence estimates could be an artefact of the markers used, and should be taken into consideration when viewing the results (Mueller 2006;Swanson et al. 2019). ...
The greater cane rat ( Thryonomys swinderianus ) is an African rodent with a wide Sub-Saharan distribution range. This species is viewed as an important protein source in many African countries. These rodents are also regularly viewed as a pest species who frequently raid croplands in agricultural settings. No phylogenetic work has to date been published on T. swinderianus from southern Africa. This paper therefore reports the first phylogenetic assessment on the species across the South African distribution range. Thirty samples were sourced from local museum collections, with one direct submission by a member of the public who found a rodent carcass identified as T. swinderianus west of its known distribution range in the Eastern Cape Province of South Africa. Two mitochondrial loci previously used in West African studies of this species were used in the current study to asses T. swinderianus population genetic diversity and phylogenetic structure across the South African distribution. A comparison to sequence data from West Africa was also performed. A divergence time estimation was conducted to further investigate the evolutionary history of the South African sub-population. Similar genetic diversity estimates were observed for the South African sub-population when compared to the West African datasets. Specimens from the eastern parts of South Africa showed higher genetic diversity estimates, possibly indicative of an initial colonisation site from eastern Africa. Two distinct phylogenetic clades were identified by Bayesian inference, forming distinct West African and South African groups. The divergence estimates showed similar ages for the T. swinderianus most recent common ancestor (MRCA) as previously reported. The MRCA estimates for the South African group identified a possible middle to late Pleistocene migratory event from eastern African into southern Africa. Further fine scale sampling across the African distribution range is however needed to provide more accurate assessments for future conservation management planning for the different sub-populations, as needed.
... World porcupines), Cavioidea (guinea pigs, maras, mocos and capybaras), Chinchilloidea (chinchillas, pacaranas, and plains viscachas), and Octodontoidea (spiny rats, chinchilla rats, degus, coruros, and tuco-tucos). Most recent phylogenies based on molecular data recovered cavioid-erethizontoid and chinchilloid-octodontoid as sister clades (Upham and Patterson, 2015;Á lvarez et al., 2017). The superfamily Chinchilloidea includes the families Chinchillidae, with the subfamilies Chinchillinae and Lagostominae, and Dinomyidae. ...
Reproductive specializations in caviomorphs (infraorder Hystricognathi), are very peculiar within the Order Rodentia. These include long gestations, the birth of offspring with an extreme degree of precociality, and short lactation periods. This study describes the embryo-placental relationship of viable implantation sites (IS) of the plains viscacha, Lagostomus maximus, after 46 post-coital days. The observations recorded in this study are comparatively discussed with those of other hystricognaths and eutherians. At this stage, the embryo resembles that of other eutherians. At this time of embryo development, the placenta exhibits a size, shape, and organization similar to that it will have in its mature state. Besides, the subplacenta is already highly folded. These characteristics are adequate to sustain the development of future precocial offspring. The mesoplacenta, a structure present in other hystricognaths and related to uterine regeneration is described for the first time in this species. This detailed description of the placental and embryonic structure contributes to the knowledge of the reproductive and developmental biology of the viscacha, as well as that of hystricognaths. These characteristics will allow testing other hypotheses related to the morphology and physiology of the placenta and subplacenta, and their relationship with the growth and development of precocial offspring in Hystricognathi.
... For all the other parameters, log Normal distributions were assumed with the values estimated from the data. The calibration points used include 17.6-28.1 million year divergence [M = 3.14, S = 0.12] for dassie rats and cane rats (Fabre et al., 2012;Patterson and Upham, 2014;Upham and Patterson, 2015), 32.6-39.4 millionyear divergence [M = 3.59, S = 0.05] for naked mole rats and cane rats (Patterson and Upham, 2014;Upham and Patterson, 2015) and 41.4-49.5 million-year divergence [M = 3.82, S = 0.04] for guinea pigs and cane rats (Poux et al., 2006;Phillips, 2015;Upham and Patterson, 2015). ...
... The calibration points used include 17.6-28.1 million year divergence [M = 3.14, S = 0.12] for dassie rats and cane rats (Fabre et al., 2012;Patterson and Upham, 2014;Upham and Patterson, 2015), 32.6-39.4 millionyear divergence [M = 3.59, S = 0.05] for naked mole rats and cane rats (Patterson and Upham, 2014;Upham and Patterson, 2015) and 41.4-49.5 million-year divergence [M = 3.82, S = 0.04] for guinea pigs and cane rats (Poux et al., 2006;Phillips, 2015;Upham and Patterson, 2015). All the calibration branches were treated as monophyletic with log Normal distributions. ...
... The calibration points used include 17.6-28.1 million year divergence [M = 3.14, S = 0.12] for dassie rats and cane rats (Fabre et al., 2012;Patterson and Upham, 2014;Upham and Patterson, 2015), 32.6-39.4 millionyear divergence [M = 3.59, S = 0.05] for naked mole rats and cane rats (Patterson and Upham, 2014;Upham and Patterson, 2015) and 41.4-49.5 million-year divergence [M = 3.82, S = 0.04] for guinea pigs and cane rats (Poux et al., 2006;Phillips, 2015;Upham and Patterson, 2015). All the calibration branches were treated as monophyletic with log Normal distributions. ...
Grasscutter (Thryonomys swinderianus) is a large-body old world rodent found in sub-Saharan Africa. The body size and the unique taste of the meat of this major crop pest have made it a target of intense hunting and a potential consideration as a micro-livestock. However, there is insufficient knowledge on the genetic diversity of its populations across African Guinean forests. Herein, we
investigated the genetic diversity, population structures and evolutionary history of seven Nigerian wild grasscutter populations together with individuals from Cameroon, Republic of Benin, and Ghana, using five mitochondrial fragments, including D-loop and cytochrome b (CYTB). D-loop haplotype diversity ranged from 0.571 (± 0.149) in Republic of Benin to 0.921 (± 0.013) in Ghana. Within Nigeria, the haplotype diversity ranged from 0.659 (± 0.059) in Cross River to 0.837 (± 0.075) in Ondo
subpopulation. The fixation index (FST), haplotype frequency distribution and analysis of molecular variance revealed varying levels of population structures across populations. No significant
signature of population contraction was detected in the grasscutter populations. Evolutionary analyses of CYTB suggests that South African population might have diverged from other populations about 6.1 (2.6–10.18, 95% CI) MYA. Taken together, this study reveals the population status and evolutionary history of grasscutter populations in the region.
... The New World hystricognath rodents (= Caviomorpha) are a particular group of mammals characterized by being morphologically and ecologically very diverse (Wood, 1955;Patton et al., 2015;Upham and Patterson, 2015;Vucetich et al., 2015a). They reached South America during the Eocene and rapidly evolved into several lineages (Poux et al., 2006;Antoine et al., 2012;Arnal and Vucetich, 2015;Boivin et al., 2019). ...
... They reached South America during the Eocene and rapidly evolved into several lineages (Poux et al., 2006;Antoine et al., 2012;Arnal and Vucetich, 2015;Boivin et al., 2019). The main reasons for their impressive evolutionary history seem related to the successful paleobiology of these rodents occupying empty niches and evolving on an island continent during most of the Cenozoic (Upham and Patterson, 2015;Vucetich et al., 2015a;Boivin et al., 2018;Arnal et al., 2020Arnal et al., , 2022. Fossil and living caviomorphs have exploited a wide array of ecological niches, inhabiting almost all environments and having generalist, arboreal, fossorial, subterranean, and aquatic habits (Verzi et al., 2010;Candela et al., 2012;Álvarez and Arnal, 2015;Patton et al., 2015;Álvarez and Ercoli, 2017;Kerber et al., 2022). ...
... In addition, they have been morphologically very diverse and have acquired a great disparity of sizes (from small to the largest rodents that ever lived on Earth) (Rinderknecht and Blanco, 2008;Vucetich et al., 2015a). Caviomorphs are grouped into four main clades (i.e., Pan-Octodontoidea sensu Arnal and Vucetich, 2015;Chinchilloidea;Cavioidea; and Erethizontoidea) and several independent fossil lineages not included in any of these four main groups (Antoine et al., 2012;Arnal and Vucetich, 2015;Patton et al., 2015;Upham and Patterson, 2015;Boivin et al., 2019;Fig. 1). ...
The study of the cranial endocast provides valuable information to understand the behavior of an organism because it coordinates sensory information and motor functions. In this work, we describe for the first time the anatomy of the encephalon of an early Miocene pan-octodontoid caviomorph rodent ( Prospaniomys priscus Ameghino, 1902) found in the Argentinean Patagonia, based on a virtual 3D endocast. This fossil rodent has an endocast morphology here considered ancestral for Pan-Octodontoidea and other South American caviomorph lineages, i.e., an encephalon with anteroposteriorly aligned elements, mesencephalon dorsally exposed, well-developed vermis of the cerebellum, and rhombic cerebral hemispheres with well-developed temporal lobes. Prospaniomys Ameghino, 1902 also has relatively small olfactory bulbs, large paraflocculi of the cerebellum, and low endocranial volume and degree of neocorticalization. Its encephalization quotient is low compared with Paleogene North American and European noncaviomorph rodents, but slightly higher than in several late early and late Miocene caviomorphs. Paleoneurological anatomical information supports the hypothesis that Prospaniomys was a generalist caviomorph rodent with terrestrial habits and enhanced low-frequency auditory specializations. The scarce paleoneurological information indicates that several endocast characters in caviomorph rodents could change with ecological pressures. This work sheds light on the anatomy and evolution of several paleoneurological aspects of this particular group of South American rodents.
... Popularly known as tuco-tucos, rodents of the genus Ctenomys comprise more than 60 species inhabiting the southern cone of South America , from Peru and Brazil in the north to the Tierra del Fuego in the south, and from the Atlantic Ocean to the west coast of the Pacific (Bidau 2015;de Freitas 2016). The origin of species allocated to this genus has been estimated to be from 10 to 3 Ma, depending on the study (Parada et al. 2011;Roratto et al. 2015;Upham and Patterson 2015;Caraballo and Rossi 2018b;de Santi et al. 2021), but it is clear that extensive and rapid cladogenesis took place around 3-1 Ma with the development of at least eight different species groups (Parada et al. 2011;de Santi et al. 2021). Although these species groups are quite stable working hypotheses, it is worth noting that these lineages were recovered via phylogenetic analysis using only a single genetic marker (mitochondrial Cytb), and no further studies (including mitochondrial and nuclear data, or at the genomic level) have been carried out to test the phylogenetic relationships among species of Ctenomys. ...
South American subterranean rodents of the genus Ctenomys (Rodentia, Ctenomyidae, tuco-tuco) are one of the most diverse genera among mammals. Recently described species, new taxonomic revisions, and new distribution range delimitation made the revision of distribution areas and conservation status of these mammals mandatory. Implementing the first part of the DAMA protocol (document, assess, monitor, act), here we compile updated sets of species distribution range maps and use these and the number of collection localities to assess the conservation status of ctenomyids. We integrate potential for conservation in protected areas, and levels of habitat transformation to revise previous conservation status assessments and propose the first assessment for all Data Deficient or not evaluated species of tuco-tucos. Our results indicate that 53 (78%) of these species are threatened and that 47 (69%) have little or no overlap with protected areas, emphasizing the urgent need to conduct conservation efforts. Here, 18 of 22 species previously classified as Data Deficient resulted in them being put in an at-risk category (VU, EN, CR). In addition, nine species that have not been previously evaluated were classified as threatened, with these two groups comprising more than 47% of the known species. These results posit that the Ctenomyidae are the rodent family with the greatest number of species at risk of extinction. Finally, a total of 33 (49%) species have been reported from three or fewer localities; all considered threatened through the approach implemented in this study. These geographically restricted taxa should be given more attention in conservation programs since the richness of this genus relies on the survival of such species.
... For the construction of the tree we used a pure-birth speciation model (the Yule process), as we did not consider extinction to have played a significant role among these closely related species. We included prior calibrations based on calibration nodes according to the phylogeny of Upham et al. [67] with included multiple markers and fossil calibration [48,67]. The node calibrations were applied for the split between Makalata and outgroups (mean = 9.7; stdev = 1.5), for the diversification of sister groups of Makalata (mean = 7.3; stdev = 1.5) and for the diversification of Makalata (mean = 9.0; stdev = 1.5) considering a normal distribution. ...
... For the construction of the tree we used a pure-birth speciation model (the Yule process), as we did not consider extinction to have played a significant role among these closely related species. We included prior calibrations based on calibration nodes according to the phylogeny of Upham et al. [67] with included multiple markers and fossil calibration [48,67]. The node calibrations were applied for the split between Makalata and outgroups (mean = 9.7; stdev = 1.5), for the diversification of sister groups of Makalata (mean = 7.3; stdev = 1.5) and for the diversification of Makalata (mean = 9.0; stdev = 1.5) considering a normal distribution. ...
... Although that study estimated the ancestral area of M. didelphoides (East Clade) to the Atlantic Forest, this is now considered an error, related to the incorrect estimation of the phylogenetic relationships of Makalata and Phyllomys. This was later resolved in Upham et al. [67]), where Amazonia region was inferred as ancestral area for Makalata. Here we corroborate the results of that later study [65], however, our broader approach reveals that the group arose through dispersal between these specific regions of northern and Eastern Amazonia. ...
Amazonian mammal diversity is exceptionally high, yet new taxonomic discoveries continue to be made and many questions remain for understanding its diversification through time and space. Here we investigate the diversification of spiny rats in the genus Makalata , whose species are strongly associated with seasonally flooded forests, watercourses and flooded islands. We use a biogeographical approach based on a mitochondrial cytochrome b gene through divergence time estimation and reconstruction of ancestral areas and events. Our findings indicate an ancient origin of Makalata for the Guiana Shield and Eastern Amazonia as ancestral area. A first cladogenetic event led to a phylogeographic break into two broader clades of Makalata through dispersal, implying a pattern of western/Eastern Amazonian clades coinciding with the Purus Arch (middle Miocene). Most of subclades we infer originated between the late Pliocene to the early Pleistocene, with few recent exceptions in the early Pliocene through dispersal and vicariant events. The hypothesis of rivers as dispersal barriers is not corroborated for Makalata , as expected for mammalian species associated with seasonally flooded environments. We identify two key events for the expansion and diversification of Makalata species: the presence of geologically stable areas in the Guiana and Brazilian shields and the transition from lacustrine conditions in western Amazonia (Acre system) to a river system, with the establishment of the Amazon River transcontinental system and its tributaries. Our results are congruent with older geological scenarios for the Amazon basin formation (Miocene), but we do not discard the influence of recent dynamics on some speciation events and, mainly, on phylogeographic structuring processes.
... The Caviomorpha is a group of endemic rodents from South America, quite diverse both in the fossil record and in the modern environments (Patton et al., 2015;Upham and Patterson, 2015;Vucetich et al., 2015a). They are known since the Eocene (Antoine et al., 2012;Boivin et al., 2017a;Boivin et al., 2021a;Arnal et al., 2022). ...
... They are known since the Eocene (Antoine et al., 2012;Boivin et al., 2017a;Boivin et al., 2021a;Arnal et al., 2022). While the lower latitudes have the higher diversity regarding extant species (Upham and Patterson, 2015), Patagonia is the richest zone in fossil specimens (Vucetich et al., 2015a). Several new localities have been found in lower latitudes recently and others have been revisited (Boivin et al., 2017a;2017b;Pérez et al., 2019;Arnal et al., 2020). ...
Cephalomyopsis hypselodontus is a member of the family Cephalomyidae, originally described based on some isolated remains from the Colhuehuapian locality of Bryn Gwyn (Chubut Province, Argentina). Some specimens from the Deseadan localities of Cabeza Blanca (Chubut Province, Argentina) and Lacayani (La Paz Department, Bolivia), first described as Cephalomyidae morphotype 2 and 3, were later included in the genus. Also, a specimen found in Arroyo Avalos (Corrientes Province, Argentina) was included in the genus, but a taxonomic revision at the species level was never conducted. In this contribution, I revise all the specimens included in the genus, as well as new specimens found in Bryn Gwyn. The new specimens include the most juvenile teeth known so far and the first complete upper tooth row known for the genus. As a result, I define a single species for the genus and discuss the implication of this new systematic proposal. The species has a wide geographical distribution and a long biochron, the longest among cephalomyids. Finally, I discuss the dissimilarities between different localities in Argentina and Bolivia and the implications in the evolutionary history of Cephalomyidae and Chinchilloidea.
