Juvenile morphology: A clue to the origins of the most mysterious of mysticetes?

The origin of the pygmy right whale (Caperea marginata) has long been one of the most vexing conundrums of marine mammal evolution. The extremely disparate skeletal structure of Caperea and a patchy fossil record have left morphology and molecules at odds: whereas most morphological analyses ally Caperea with right whales (Balaenidae), most molecular studies instead suggest a close relationship with rorquals (Balaenopteridae) and grey whales (Eschrichtiidae). The morphological evidence supporting a Caperea-balaenid clade consists of several shared features of the skull and mandible, as traditionally observed in adult individuals. Here, we show that at least two of these features, the ascending process of the maxilla and the coronoid process, arise from substantially different precursors early during ontogeny and therefore likely do not represent genuine synapomorphies. Both of these juvenile morphologies have adult counterparts in the fossil record, thus indicating that the ontogenetic variation in the living species may be a genuine reflection of differing ancestral states. This new evidence contradicts previous morphological hypotheses on the origins of Caperea and may help to reconcile morphological and molecular evidence.     

An opilioacarid mite in Cretaceous Burmese amber

A fossil opilioacarid mite (Parasitiformes: Opilioacarida) in Burmese amber is described as ?Opilioacarus groehni sp. nov. This ca. 99 Ma record (Upper Cretaceous: Cenomanian) represents only the third fossil example of this putatively basal mite lineage, the others originating from Eocene Baltic amber (ca. 44–49 Ma). Our new record is not only the oldest record of Opilioacarida, but it is also one of the oldest examples of the entire Parasitiformes clade. The presence of Opilioacarida—potentially Opiloacarus—in the Cretaceous of SE Asia suggests that some modern genus groups were formerly more widely distributed across the northern hemisphere, raising questions about previously suggested Gondwanan origins for these mites.     

Earliest and first Northern Hemispheric hoatzin fossils substantiate Old World origin of a “Neotropic endemic”

The recent identification of hoatzins (Opisthocomiformes) in the Miocene of Africa showed part of the evolution of these birds, which are now only found in South America, to have taken place outside the Neotropic region. Here, we describe a new fossil species from the late Eocene of France, which constitutes the earliest fossil record of hoatzins and the first one from the Northern Hemisphere. Protoazin parisiensis gen. et sp. nov. is more closely related to South American Opisthocomiformes than the African taxon Namibiavis and substantiates an Old World origin of hoatzins, as well as a relictual distribution of the single extant species. Although recognition of hoatzins in Europe may challenge their presumed transatlantic dispersal, there are still no North American fossils in support of an alternative, Northern Hemispheric, dispersal route. In addition to Opisthocomiformes, other avian taxa are known from the Cenozoic of Europe, the extant representatives of which are only found in South America. Recognition of hoatzins in the early Cenozoic of Europe is of particular significance because Opisthocomiformes have a fossil record in sub-Saharan Africa, which supports the hypothesis that extinction of at least some of these “South American” groups outside the Neotropic region was not primarily due to climatic factors.     

Skeletal remains of a diminutive primate from the Paleocene of Germany

Most living mammal orders, including our own, started their career during the first 10 million years of the Cenozoic, the Age of Mammals. The fossil record documents that early Paleogene adaptive radiations of various clades included tiny species of the size of living shrews. Remains of particularly diminutive limb bones are described from the late Paleocene site of Walbeck, Sachsen-Anhalt. Discovered in 1939, it has remained the only known Paleocene mammal-bearing locality from Germany. The remains are referred to the family Adapisoriculidae, which is considered on the basis of the present postcranial evidence to represent plesiadapiform primates rather than alleged lipotyphlan insectivores as previously proposed. The Walbeck fossils compete with the Early Eocene species Toliapina vinealis from Europe and Picromomys petersonorum from North America for the status of the smallest known primate, fossil and living. Their estimated body weights are as small as 10 g. The limb bones show features related to enhanced flexion at the elbow and hip joint, suggesting arboreal habits and environments such as terminal branches. The diminutive size and tooth morphology suggest feeding on small insects and other invertebrates. Postcranials are important to assess early radiations, such tiny specimens as the present ones are extremely scarce in the fossil record, however.     

Eocene bunoselenodont Artiodactyla from southern Thailand and the early evolution of Ruminantia in South Asia

Although Asia is thought to have played a critical role in the basal radiation of Ruminantia, the fossil record of early selenodont artiodactyls remains poorly documented in this region. Dental remains of a new bunoselenodont artiodactyl are described from the late Eocene of Krabi, southern Thailand. This new form, Krabitherium waileki gen. et sp. nov, is tentatively referred to the Tragulidae (Ruminantia) on the basis of several dental features, including a weak Tragulus fold and the presence of a deep groove on the anterior face of the entoconid. Although this new form is suggestive of the enigmatic ?Gelocus gajensis Pilgrim 1912 from the “base of the Gaj” (lower Chitarwata Formation) of the Bugti Hills (Central Pakistan), K. waileki most likely represents an early representative of a relatively bunodont group of tragulids that includes the genus Dorcabune, known from the Miocene of south Asia. This addition to the Eocene record of early ruminants attests to the antiquity of the group in Southeast Asia and lends support to the hypothesis that the Tragulidae represents one of the first offshoots in the evolutionary history of Ruminantia.     

A new fossil thryonomyid from the Late Miocene of the United Arab Emirates and the origin of African cane rats

Cane rats (Thryonomyidae) are represented today by two species inhabiting sub-Saharan Africa. Their fossil record is predominately African, but includes several Miocene species from Arabia and continental Asia that represent dispersal events from Africa. For example, Paraulacodus indicus, known from the Miocene of Pakistan, is closely related to living Thryonomys. Here we describe a new thryonomyid, Protohummus dango, gen. et sp. nov., from the late Miocene Baynunah Formation of the United Arab Emirates. The new thryonomyid is less derived than “Thryonomys” asakomae from the latest Miocene of Ethiopia and clarifies the origin of crown Thryonomys and the evolutionary transition from Paraulacodus. A phylogenetic analysis shows Protohummus dango to be morphologically intermediate between Paraulacodus spp. and extinct and living Thryonomys spp. The morphological grade and phylogenetic position of Protohummus dango further supports previous biochronological estimates of the age of the Baynunah Formation (ca. 6–8 Ma).     

An ‘ameridelphian’ marsupial from the early Eocene of Australia supports a complex model of Southern Hemisphere marsupial biogeography

Recent molecular data strongly support the monophyly of all extant Australian and New Guinean marsupials (Eomarsupialia) to the exclusion of extant South American marsupials. This, together with available geological and fossil evidence, has been used to argue that the presence of marsupials in Australia is simply the result of a single dispersal event from South America during the latest Cretaceous or Palaeocene, without subsequent dispersals between the two continents. Here, I describe an isolated ankle bone (calcaneus) of a metatherian from the early Eocene Tingamarra Local Fauna in northeastern Australia. Strikingly, this specimen, QM F30060, lacks the ‘continuous lower ankle joint pattern’ (CLAJP), presence of which is a highly distinctive apomorphy of the marsupial clade Australidelphia, which includes Eomarsupialia, the living South American microbiotherian Dromiciops and the Tingamarran fossil marsupial Djarthia. Comparisons with a range of marsupials and stem-metatherians strongly suggest that the absence of the CLAJP in QM F30060 is plesiomorphic, and that this specimen represents the first unequivocal non-australidelphian (‘ameridelphian’) metatherian known from Australia. This interpretation is confirmed by phylogenetic analyses that place QM F30060 within (crown-group) Marsupialia, but outside Australidelphia. Based on these results, the distribution of marsupials within Gondwana cannot be explained by simply a single dispersal event from South America and Australia. Either there were multiple dispersals by marsupials (and possibly also stem-metatherians) between South America and Australia, in one or both directions, or, alternatively, there was a broadly similar metatherian fauna stretching across southern South America, Antarctica and Australia during the Late Cretaceous–early Palaeogene.     

A giant termite from the Late Miocene of Styria, Austria (Isoptera)

A giant termite is described and figured from the Late Miocene of the Styrian Basin in southeastern Austria. Gyatermes styriensis gen. n. et sp. n. is represented by a relatively complete forewing, with basal scale. The fossil approximates in size the largest of all termites today and is the largest fossil termite on record. The presence of this species in the Late Miocene fauna of Europe indicates that climatic conditions were appropriate for the persistence of species and colonies requiring relatively stable, warm conditions. The genus is primitive in overall features but shares some similarity with the dampwood termites.     

The oldest haplogyne spider (Araneae: Plectreuridae), from the Middle Jurassic of China

New fossil spiders (Arachnida: Araneae) from Middle Jurassic (ca. 165 Ma) strata of Daohugou, Inner Mongolia, China are described as Eoplectreurys gertschi gen. et sp. nov. and referred to the modern haplogyne family Plectreuridae. This small family is restricted to southwestern USA, Mexico, and the adjacent Caribbean area today and hitherto has only a sparse Cenozoic fossil record. The morphology of Eoplectreurys is remarkably similar to modern forms and thus demonstrates great evolutionary conservatism. This new discovery not only extends the fossil record of the family by at least 120 Ma to the Middle Jurassic but also supports the hypothesis of a different distribution of the family in the past than today and subsequent extinction over much of its former range.     

Artiodactyls from the Pondaung Formation (Myanmar): new data and reevaluation of the South Asian Faunal Province during the Middle Eocene

Although Asia is thought to have played a critical role in the radiation of artiodactyls, the fossil record of stem selenodonts (“dichobunoids”) remains dramatically poor in tropical Asian regions. In this study, we report a new dichobunid genus and species Cadutherium kyaukmagyii and a new basal ruminant genus and species Irrawadymeryx pondaungi, from the late Middle Eocene Pondaung Formation, Central Myanmar. Although the scarcity of the present material prevents any attempts to investigate the phylogenetic relationships of Cadutherium with contemporaneous forms from other Holarctic landmasses, this new form shed new light on the diversity of these small rabbit-like ungulates during a key period of their evolutionary history. Reexamination of the small-bodied artiodactyls from Pondaung leads us to propose new identifications of certain published specimens and, in turn, to investigate the temporal and geographic distribution of taxa recognized in the Pondaung Formation. Although fragmentary, these potential new taxa reveal an unsuspected diversity of small forms among artiodactyls of Pondaung. This addition to the Eocene record of dichobunoids and early ruminants provides further insight in the diversity of dental patterns among small artiodactyls from the Pondaung Formation and attests to the antiquity of these groups in Southeast Asia.     

Cretaceous choristoderan reptiles gave birth to live young

Viviparity (giving birth to live young) in fossil reptiles has been known only in a few marine groups: ichthyosaurs, pachypleurosaurs, and mosasaurs. Here, we report a pregnant specimen of the Early Cretaceous Hyphalosaurus baitaigouensis, a species of Choristodera, a diapsid group known from unequivocal fossil remains from the Middle Jurassic to the early Miocene (about 165 to 20 million years ago). This specimen provides the first evidence of viviparity in choristoderan reptiles and is also the sole record of viviparity in fossil reptiles which lived in freshwater ecosystems. This exquisitely preserved specimen contains up to 18 embryos arranged in pairs. Size comparison with small free-living individuals and the straight posture of the posterior-most pair suggest that those embryos were at term and had probably reached parturition. The posterior-most embryo on the left side has the head positioned toward the rear, contrary to normal position, suggesting a complication that may have contributed to the mother’s death. Viviparity would certainly have freed species of Hyphalosaurus from the need to return to land to deposit eggs; taking this advantage, they would have avoided intense competition with contemporaneous terrestrial carnivores such as dinosaurs.     

关于浙东塘上组的时代问题

浙东塘上组中、下部火山岩的沉积夹层中首次发现?Halysestheria叶肢介及孢粉化石,并找到Pseudofrcneloysis parceramosa与P.cf.rapillosa为主的植物化石。本文综合各门类化石所反映的地质时代,认为浙东塘上组应归属早白垩世晚期。这与剖面上获得的同位素年龄值(110 Ma)相吻合。塘上组层位与邻区石帽山群上组、禾口组(闽),周家店组(赣东),徽州组上部(皖南)及葛村组上部(江苏)相当。     

Brainy stuff of long-gone dogs: a reappraisal of the supposed Canis endocranial cast from the Pliocene of Poland

The pre-Quaternary fossil record of Canis in the Old World is scarce, and the first appearance of this genus in Europe remains an enigma. Amongst the oldest fossils assigned to this genus, there is a natural cast of the brain (endocast) collected in W??e 1, Poland, from Pliocene deposits dated between 3.3 and 4.0 Ma. We reexamined this specimen and found that it differs from the brain of Canis in having its region medial to the coronal sulcus heart-shaped in dorsal view, its region rostral to the presylvian sulcus shorter and less constricted laterally, and its cerebellum less overlapped by the cerebrum and lacking a lateral twist of the posterior vermis. We identified this fossil, as well as another fossil canid endocast from W??e 1, as representing the raccoon dog genus Nyctereutes. The previously reported presence of Canis in W??e 1 is therefore not confirmed. Specifically, both endocasts can be referred to N. donnezani because this is the only species of Nyctereutes that has been recognised in this locality on the basis of craniomandibular and dental fossils. Our study represents a taxonomic application of comparative neuroanatomical and palaeoneurological data, an approach that may become increasingly useful with the growing knowledge of the endocranial morphology of fossil mammals.     

Europe's last Mesozoic bird

Birds known from more than isolated skeletal elements are rare in the fossil record, especially from the European Mesozoic. This paucity has hindered interpretations of avian evolution immediately prior to, and in the aftermath of, the Cretaceous-Tertiary (K-T) extinction event. We report on a specimen of a large ornithurine bird (closely related to Ichthyornis) from the uppermost Cretaceous (Maastricht Formation) of Belgium. This is the first record of a bird from these historic strata and the only phylogenetically informative ornithurine to be recovered from the Mesozoic of Europe. Because this new specimen was collected from 40 m below the K-T boundary (approximate age of 65.8 Ma), it is also the youngest non-neornithine (=non-modern) bird known from anywhere in the world.     

Biomolecules preserved in ca. 168 million year old fossil conifer wood

Biomarkers are widely known to occur in the fossil record, but the unaltered biomolecules are rarely reported from sediments older than Paleogene. Polar terpenoids, the natural products most resistant to degradation processes, were reported mainly from the Tertiary conifers, and the oldest known are Cretaceous in age. In this paper, we report the occurrence of relatively high concentrations of ferruginol derivatives and other polar diterpenoids, as well as their diagenetic products, in a conifer wood Protopodocarpoxylon from the Middle Jurassic of Poland. Thus, the natural product terpenoids reported in this paper are definitely the oldest polar biomolecules detected in geological samples. The extracted phenolic abietanes like ferruginol and its derivatives (6,7-dehydroferruginol, sugiol, 11,14-dioxopisiferic acid) are produced only by distinct conifer families (Cupressaceae s. l., Podocarpaceae and Araucariaceae), to which Protopodocarpoxylon could belong based on anatomical characteristics. Therefore, the natural product terpenoids are of great advantage in systematics of fossil plant remains older than Paleogene and lacking suitable anatomical preservation.     

The oldest African bat from the early Eocene of El Kohol (Algeria)

The Afro-Arabian Paleogene fossil record of Chiroptera is very poor. In North Africa and Arabia, this record is limited, thus far, to a few localities mainly in Tunisia (Chambi, late early Eocene), Egypt (Fayum, late Eocene to early Oligocene), and Sultanate of Oman (Taqah, early Oligocene). It consists primarily of isolated teeth or mandible fragments. Interestingly, these African fossil bats document two modern groups (Vespertilionoidea and Rhinolophoidea) from the early Eocene, while the bat fossil record of the same epoch of North America, Eurasia, and Australia principally includes members of the ??Eochiroptera.?? This paraphyletic group contains all primitive microbats excluding modern families. In Algeria, the region of Brezina, southeast of the Atlas Mountains, is famous for the early Eocene El Kohol Formation, which has yielded one of the earliest mammalian faunas of the African landmass. Recent fieldwork in the same area has led to the discovery of a new vertebrate locality, including isolated teeth of Chiroptera. These fossils represent the oldest occurrence of Chiroptera in Africa, thus extending back the record of the group to the middle early Eocene (Ypresian) on that continent. The material consists of an upper molar and two fragments of lower molars. The dental character association matches that of ??Eochiroptera.?? As such, although very fragmentary, the material testifies to the first occurrence of ??Eochiroptera?? in Algeria, and by extension in Africa. This discovery demonstrates that this basal group of Chiroptera had a worldwide distribution during the early Paleogene.     

Spine anatomy reveals the diversity of catfish through time: a case study of Synodontis (Siluriformes)

Synodontis (Mochokidae, Siluriformes) is a freshwater catfish endemic to Africa. The 118 extant species are present in almost all hydrographic basins. Some species are restricted to a single stream, whereas others have a vast distribution. Synodontis is known in the fossil record since the Miocene, and its history depends on the connections among African basins through time. The identification of species in the fossil record is essential to reconstruct this historical pattern. Catfish pectoral and dorsal spines are robust, they preserve well and they form most of the fossil remains for the genus Synodontis. Unfortunately, the criteria for the identification of extant Synodontis species are not applicable to fossil specimens. Here, we define 11 original morphological characters that permit to discriminate four extant species from the Chad-Chari hydrographic system. Six of these characters are defined on pectoral spines and five on dorsal spines. We then show that these characters can be used successfully for identifying fossil specimens. In particular, we present a case study in which we identify Synodontis cf. schall and Brachysynodontis cf. batensoda in the hominid-bearing sector Toros-Menalla (Late Miocene, northern Chad). We show that spine anatomy can be a powerful tool to recognise catfish species through time and thus to identify historical diversity pattern.     

生物卵化石研究进展简述

卵生是动物界最普遍的繁殖方式,卵的孵化对繁殖季节突发的气候变化响应敏感,孵化成败又与生物种群数量变动和群落演替密切相关,因此卵化石具有重要的古生物学、古气候学、古生态学研究价值。但由于卵生动物种类十分丰富,卵形态特征多样,研究领域广泛,有必要总结梳理卵化石的研究进展。本文通过对主要卵生动物类群卵的形态特征,以及卵化石在古生物学、古气候学、古生态学方面研究进展的回顾,发现卵化石的研究主要集中在脊椎动物类群,为脊椎动物演化提供了重要证据,但是由于脊椎动物卵化石通常难以建立连续的长序列记录,其古生态学和古气候学研究极为不足。然而,无脊椎动物卵化石由于数量丰富,具有统计意义,其在古生态学、古气候学研究领域具有重要意义,但是其在古生物学,包括种属鉴定等方面的研究需要加强。在无脊椎动物中,蜗牛及其卵化石在黄土-古土壤地层中保存丰富且地层分布连续,最有可能建立卵化石的长序列。通过现代过程研究,明确蜗牛卵的气候指示意义,建立第四纪蜗牛卵化石长序列,发挥蜗牛卵化石的古气候学和古生态学研究价值,是亟需开展的研究工作。     

Was endothermy in amniotes induced by an early stop in growth during ontogeny?

Endothermy and its evolution are still an unresolved issue. Here, we present a model which transforms an ectothermic amniote (ancestor) into a derived amniote (descendant) showing many characteristics seen in extant endothermic birds and mammals. Consistent with the fossil record within the ancestral lineages of birds and mammals, the model assumes that mutations in genes which get active during ontogeny and affect body growth resulted in a reduced asymptotic body size and an early growth stop of the descendant. We show that such a postulated early growth stop in the descendant simultaneously increases the growth rate and metabolic rate, and also changes six life history traits (offspring mass, annual clutch/litter mass, number of offspring per year, age and mass at which sexual maturity is reached, age at which the individual is fully grown) of the descendant compared to a similar-sized ancestor. All these changes coincide with known differences between recent ectothermic and endothermic amniotes. We also elaborate many other differences and similarities in biological characteristics supporting the early growth stop. An early stop in growth during ontogeny thus could have played a key role in the evolution of endothermy within the reptilia and therapsids. It generated variability in characteristics of ancestral ectotherms, which was subject to natural selection in the past and resulted in many adaptations linked to endothermy in today’s birds and mammals.