The Influence of Modularity on Cranial Morphological Disparity in Carnivora and Primates (Mammalia)

Background

Although variation provides the raw material for natural selection and evolution, few empirical data exist about the factors controlling morphological variation. Because developmental constraints on variation are expected to act by influencing trait correlations, studies of modularity offer promising approaches that quantify and summarize patterns of trait relationships. Modules, highly-correlated and semi-autonomous sets of traits, are observed at many levels of biological organization, from genes to colonies. The evolutionary significance of modularity is considerable, with potential effects including constraining the variation of individual traits, circumventing pleiotropy and canalization, and facilitating the transformation of functional structures. Despite these important consequences, there has been little empirical study of how modularity influences morphological evolution on a macroevolutionary scale. Here, we conduct the first morphometric analysis of modularity and disparity in two clades of placental mammals, Primates and Carnivora, and test if trait integration within modules constrains or facilitates morphological evolution.

Principal Findings

We used both randomization methods and direct comparisons of landmark variance to compare disparity in the six cranial modules identified in previous studies. The cranial base, a highly-integrated module, showed significantly low disparity in Primates and low landmark variance in both Primates and Carnivora. The vault, zygomatic-pterygoid and orbit modules, characterized by low trait integration, displayed significantly high disparity within Carnivora. 14 of 24 results from analyses of disparity show no significant relationship between module integration and morphological disparity. Of the ten significant or marginally significant results, eight support the hypothesis that integration within modules constrains morphological evolution in the placental skull. Only the molar module, a highly-integrated and functionally important module, showed significantly high disparity in Carnivora, in support of the facilitation hypothesis.

Conclusions

This analysis of within-module disparity suggested that strong integration of traits had little influence on morphological evolution over large time scales. However, where significant results were found, the primary effect of strong integration of traits was to constrain morphological variation. Thus, within Primates and Carnivora, there was some support for the hypothesis that integration of traits within cranial modules limits morphological evolution, presumably by limiting the variation of individual traits.     

Humerus development in moles (Talpidae,Mammalia)

The humerus of fossorial moles has a highly derived anatomy, reflecting the ecological specialization of these animals for digging. It is short and broad, with enlarged muscle attachment sites and pronounced articulations compared to non‐fossorial sister taxa and other mammals. Both condyles are rotated in opposite directions, resulting in a torsion which is unique among eutherian mammals. The development of this exceptional bone was studied in embryonic stages of the fossorial Iberian mole (Talpa occidentalis) from mesenchymal condensation to incipient ossification based on histological serial sections using 3D reconstruction methods. For comparison, embryonic stages of the semi‐fossorial Japanese shrew mole (Urotrichus talpoides) as well as a sister taxon of moles, the terrestrial North American least shrew (Cryptotis parva), were studied. Results show that the humerus of Talpa already shows its derived anatomy with broadened muscle attachment sites and distinct articulations at early cartilaginous stages, when ossification has just started in the mid‐diaphyseal region. The torsion takes place simultaneously with the medial rotation of the forelimbs. The supracondylar foramen is closed in all studied Talpa embryos, but patent in Cryptotis and Urotrichus. This is an example of developmental penetrance, suggesting that variation of adult elements can be found at early stages as well.     

A Morphological Basis for Assessing the Phylogeny of the "Tenrecoidea" (Mammalia, Lipotyphla)

A phylogenetic analysis of 35 mammalian taxa focusing on the lipotyphlan family Tenrecidae, based on 193 morphological character states across 71 characters, is undertaken to test several hypotheses of lipotyphlan relationships, including monophyly of the Lipotyphla, Tenrecidae, Malagasy Tenrecidae, and Caribbean Lipotyphla. Explicit tests of these hypotheses are central to understanding larger issues concerning Malagasy and Caribbean biogeography, in addition to mammalian phylogeny. Methodologically, several different parameters are created with which to determine the sensitivity of resulting clades to initial assumptions about a posteriori character weighting, missing data, and multistate character ordering. Clades produced by this data set that appear despite perturbations in these parameters and that are supported by other confidence-assessment techniques contradict Malagasy tenrecid monophyly and the association of soricids with the Caribbean taxon Solenodon. Results regarding tenrecid and lipotyphlan monophyly are more ambiguous and depend on certain assumptions regarding treatment of character ordering, weighting, and missing data. An alternative phylogeny supporting an African mammal clade receives no support from the data set discussed herein.     

Skeletal adaptations and phylogeny of the oldest mole Eotalpa (Talpidae,Lipotyphla, Mammalia) from the UK Eocene: the beginning of fossoriality in moles

The oldest talpid, Eotalpa, was previously known only from isolated cheek teeth from the European late Middle Eocene to earliest Oligocene. Screenwashing of Late Eocene sediments of the Hampshire Basin, UK, has yielded cranial and postcranial elements: maxilla, dentary, ulna, metacarpals, distal tibia, astragalus, calcaneum, metatarsals and phalanges. In addition to M_1–2 myotodonty, typical talpid features are as follows: ulna with long medially curved olecranon and deep abductor fossa and astragalar body with lateral process. However, Eotalpa retains certain soricid‐like primitive states (M¹ preparacrista, P⁴ with prominent mesiolingual protocone lobe, strongly angled astragalar neck and calcaneum with no space for a cuboid medial process) not found in modern talpids. Eotalpa is more derived than the most primitive living talpid Uropsilus in having lost the M^1–2 talon shelf, developed a convex radial facet on the ulna, an incipient proximal olecranon crest, relatively shorter metapodials and depressed manual unguals. Its astragalus with medial trochlear ridge taller than the lateral one and massive medial plantar process is typical of the Lipotyphla. Eotalpa lacks synostosis of tibia and fibula, found in other Talpidae, Soricidae and Erinaceidae, suggesting that synostosis in these groups has been independently acquired. Cladistic analysis places Eotalpa as stem member of the Talpidae and shows that much homoplasy arose during the early evolution of the family. Ground dwelling in Eotalpa is indicated by the following: astragalus with a medially dipping head, curved in a single plane; calcaneum with distal peroneal process and strongly overlapping ectal and sustentacular facets; and matching sized ectal and sustentacular facets on calcaneum and astragalus. These features would have restricted ankle mobility. Ungual and metatarsal shape and ulnar structure suggest a primitive stage in fossorial evolution and argue against a semiaquatic precursor stage in talpid fossoriality. Shrew‐moles may represent a reversal to surface foraging rather than an intermediate stage in fossoriality.     

Dentition Anomalies in Nesophontidae (Lipotyphla,Mammalia) from the Pleistocene of Cuba

Doklady Biological Sciences - The study of the remains of Nesophontes micrus Allen, 1917 and N. major Arredondo, 1970 from El Abrón Cave (Republic of Cuba, Pinar del Río...     

Dental Replacement in Nesophontidae (Lipotyphla,Mammalia) from the Pleistocene of Cuba

Doklady Biological Sciences - The presence of deciduous premolars and erupting C1, P2, P4, I1, I2, I3, P2, and P4 in Nesophontidae is established for the first time on the fossil remains of...     

Systematics and macroevolution of extant and fossil scalopine moles (Mammalia,Talpidae)

Scalopini is one of the two fully fossorial mole tribes in the family Talpidae, with remarkable adaptations to subterranean lifestyles. Most living Scalopini species are distributed in North America while a sole species occurs in China. On the other hand, scalopine fossils are found in both Eurasia and North America from upper Oligocene strata onwards, implying a complex biogeographical history. The systematic relationships of both extant and fossil Scalopini across North America and Eurasia are revised by conducting phylogenetic analyses using a comprehensive morphological character matrix together with 2D geometric–morphometric analyses of the humeral shape, with a specific emphasis on Mioscalops, a genus commonly found in North America and formerly known as Scalopoides. Our phylogenetic analyses support the monophyly of the tribe Scalopini as well as a proposed two‐subtribe‐division scenario of Scalopini (i.e. Scalopina and Parascalopina), although Proscapanus could not be assigned to either subgenus. Our geometric–morphometric analyses indicate that the European Mioscalops from southern Germany should be allocated to Leptoscaptor, which in turn implies that Mioscalops may be endemic to North America and never arrived in Europe. Examination of biogeographical patterns does not unambiguously determine the geographical origin of Scalopini. Nevertheless, it does support multiple transcontinental colonization events across Asia, Europe and North America. Scapanulus oweni, distributed in central China, is the only remaining representative of one of those out‐of‐North‐America migrations, whereas scalopine moles are common in North America nowadays with up to five species.     

Allometry and chromosomal speciation of the casiraguas Proechimys (Mammalia, Rodentia)

Morphometric characters (linear measurements) of the skull and mandible of the rodent Proechimys occurring in Venezuela and Columbia were investigated through multivariate techniques in order to describe static allometry and to relate allometric patterns to the recent evolution of these taxa. At least five species originated during the recent Pleistocene period in the upper Orinoco basin, all characterized by different karyotypes, one of them (P. guairae) being a Rassenkreis of karyomorphs. Species are characterized by unique static allometric patterns and the study of these patterns suggests a phylogenetic rather than an ecogenetic origin for these patterns; modifications in the shape of the skull and the mandible have originated during phyletic speciation and there is no apparent sign of functional adaptation.     

Evolution of Oligo-Miocene talpids (Mammalia,Talpidae) in Europe: focus on the genera Myxomygale and Percymygale n. gen.

Abstract

New material recovered in the Oligocene locality St-Martin-de-Castillon (Vaucluse, France; MP24) provides a better knowledge of the characteristics of the species vauclusensis in its type-locality, hitherto assigned to the genus Myxomygale (Talpinae, tribe Urotrichini). In Europe, the species assigned to Myxomygale range from Late Eocene/Early Oligocene to the end of the Middle Miocene (MN 7/8). However noticeable differences can be observed in mandibles of these taxa, sometimes even coexisting in the same localities. We propose for the plesiomorphic branch (including M. vauclusensis and M. minor) a new genus, Percymygale, closely related to Myxomygale. Percymygale is consequently also assigned to the tribe Urotrichini. Today, the tribe Urotrichini (American and Japanese shrew-moles) is composed of terrestrial, semi-fossorial species, not well adapted to digging but able to climb small bushes, and foraging in grasslands, forests and covered landscapes. As a result, their limbs protrude laterally from the body (unlike in moles) and their humeri are usually longer with very limited adaptations to digging. Humeri are poorly known for Myxomygale and only fragmentary humeri are known for Percymygale n. gen. making comparisons difficult. However the muzzle development in Percymygale and Myxomygale suggests that Myxomygale was perhaps a better burrower than Percymygale.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:E0BDC0FC-ABA2-4A84-AE76-06B3433B432E

http://www.zoobank.org/urn:lsid:zoobank.org:act:17E4DD37-24A4-4C7A-A7FEB421CF90F89C     

Functional,Morphological, and Evolutionary Characterization of Hearing in Subterranean,Eusocial African Mole-Rats

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Notes on type specimens of European Miocene Talpidae and a tentative classification of old world Tertiary Talpidae (Insectivora: Mammalia)

Survey of the type of the Miocene Talpidae of Europe results in the allocation of several of the types to new or different genera. Three genera and one species previously referred to the family do not belong there. The diversity of Miocene talpids indicates an influx of generic stocks into Western Europe in the early Miocene, probably from Asia. New data provide a basis for a tentative phylogeny and classification of the European genera.     

A composite species-level phylogeny of the 'Insectivora' (Mammalia: Order Lipotyphla Haeckel, 1866)

The first MRP (matrix representation with parsimony) supertree phylogeny of the Lipotyphla is presented, covering all the families that were considered to make up the traditional mammalian order Insectivora. The phylogeny does not examine relationships within the shrew subfamily Crocidurinae, but all other taxa are considered at the species level, drawing upon 41 years of systematic literature and combining information from 47 published sources. The MRP technique is also critically discussed. This study will be of use to comparative biology studies of the Lipotyphla (or of mammals as a whole) and is a rigorous review of past systematic work, as well as clearly demonstrating our current level of knowledge. The supertree clearly details a strong imbalance in phylogenetic understanding across the taxon: a great deal is known about the hedgehogs and gymnures (Erinaceidae), the New World moles (Talpidae), Palaearctic species of Sorex (subgenus Sorex ) and the relationships between genera of red-toothed shrews (Soricinae). The supertree, however, clearly shows areas where our knowledge is conflicting or non-existent, and these gaps do not always correspond to obscure species: nothing is known about the systematics of Old World mole genera. Also very little is known about golden moles (Chrysochloridae) and the shrew-tenrec genus Microgale , some of the most threatened mammals on Earth.     

First record of an upper deciduous molar in Desmanella (Uropsilinae,Talpidae, Mammalia)

The dP4 of Desmanella engesseri Ziegler, 1985 from a maxillary which includes the P2 and P3 in crypt, the P4 in eruption and fully erupted dP4 and M1, is described from Petersbuch 28 (Germany; Lower Miocene, MN3/4). The maxillary was studied using X-ray microtomography to make detailed images of the internal and external features of the sample. This is the first record of a dP4 from Desmanella Engesser, 1972. Its shape is unique for fossil talpids, possessing the apomorphic feature of replacing the protocone with a large lingual cingulum. The functional use of deciduous teeth and the process that led to the complete loss of milk teeth in extant talpids are discussed.     

New data on the distribution and genetic structure of Greek moles of the genus Talpa (Mammalia,Talpidae)

In this work, we employed molecular markers and confirmed the occurrence of two mole species, Talpa stankovici and Talpa europaea in Greece. For the first species, all analyses revealed three major phylogroups, exhibiting great genetic divergence, possibly due to a vicariant event. This event was probably the Peloponnisos’ insulation during the Pliocene and the following sea level fluctuations. A scenario of stable, large‐sized populations for a long period rather than rapid growth from small‐sized populations or founder events is supported. Additionally, T. stankovici’s distribution area is extended to a southernmost limit. For T. europaea there is evidence of low genetic divergence between Greek and Central and North European populations.     

Evolutionary trends in Mio-Pliocene Leporinae, based onTrischizolagus (Mammalia, Lagomorpha)

New material ofTrischizolagus dumitrescuae from Moldova and Ukraine is described. The variation of p3 inTrischizolagus shows the gradual shift of morphotype frequencies from the ‘Hypolagus’ pattern in Turolian through the mixture of three patterns (including ‘Nekrolagus’ morphotype) in Early Ruscinian to the dominant ‘Alilepus’ pattern in the Late Ruscinian samples. These transformations took place parallel to that of the North AmericanNekrolagus. Probably North AmericanSylvilagus, Brachylagus, andRomerolagus had an North American origin fromNekrolagus, whereas Eurasiatic and AfricanOryctolagus, Caprolagus, Nesolagus, andPoelagus could have originated in the Old World fromTrischizolagus.     

Blarinoides aliciae sp. nov., a new Soricidae (Mammalia,Lipotyphla) from the Pliocene of Spain

A new species of Blarinoides (Soricidae, Mammalia), Blarinoides aliciae, is described from the Pliocene of Tollo de Chiclana (Guadix Basin, southeastern Spain). It is notably smaller than the single species of this genus known until now, B. mariae. B. aliciae is recorded from several other Spanish localities, but the sample from Tollo de Chiclana-3 is the most numerous. B. aliciae proves the simultaneous existence of two different species of Blarinoides in Europe during the Pliocene: one of large size in central and eastern Europe, and another one of small size in Iberia.     

白尾鼹(鼹科: 哺乳纲)下颌骨几何形态测量分析及地理分化研究

白尾鼹属为东洋界单型属,主要分布于中国西南山地、印度阿萨姆地区、孟加拉国、缅甸北部和老挝等地。由于白尾鼹分布区范围内地形、气候和生境十分复杂,很可能导致物种的地理分化。为此我们查看了分布区之内18 个地区的49 号标本的下颌骨,并基于几何形态测量的方法进行分析比较。结果显示所有的标本按照地理分布可分为3 组(滇东北、横断山南段以及印度)。3 组标本间的形态差异主要表现在水平枝上,其中下臼齿齿列的长度、下颌骨水平枝下缘的弯曲度以及水平枝中部高度差异最为明显,而上升枝对3 个地理居群的区分能力较弱。其中滇东北标本的下颌骨最为平直,下臼齿列长度最短;而横断山居群的下颌骨弯曲度最大,下臼齿列最长。根据以上结果,我们推测3 个下颌骨形态有明显差异的地理居群可能代表了3 个不同的地理亚种或是不同的种。但这仍需要结合上颌骨的形态差异和遗传结构分析加以证实。