Remarkably preserved annelid worms from the La Meseta Formation (Eocene), Seymour Island, Antarctica

Abstract: Worm tubes, which exhibit the replaced tube-lining membrane, have been collected from the lowermost Lower Eocene Acantilados Allomember of the La Meseta Formation, Seymour Island, Antarctica. The discovery represents the oldest examples of preservation of the tube-lining membrane of tube-dwelling Polychaeta in the fossil record. A new genus and species, Caprascolex antarcticus , are described. The specimens are preserved as thin coatings of amorphous iron oxide on the inner surface of the moulds interpreted to be the replaced tube-lining membrane. Examination of the rarely described tube-lining mucosoid membrane in extant polychaetes shows that the fossils are nearly identical in morphology and scale to extant forms. These fossils record in remarkable detail the morphology of the tube-lining membrane, which appears to be composed of growth bands formed as the worm constructed the tube. The tube-lining is believed to have been originally preserved as pyrite, with subsequent oxidation to iron oxide. The tube-lining membrane of worm tubes possibly is known from only one other fossil occurrence.     

Skates and rays (Elasmobranchii,Batomorphii) from the Eocene La Meseta and Submeseta formations,Seymour Island,Antarctica

Abstract

Eocene deposits of the famous La Meseta Formation of Seymour Island, Antarctic Peninsula, yielded the most diverse Paleogene fossil elasmobranch association of the Southern Hemisphere. In this assemblage, sharks clearly dominate the fauna, whereas batoids are very rare components. Herein, we describe two new taxa of cold water tolerant skates, Marambioraja leiostemma gen. et sp. nov., and Mesetaraja maleficapelli gen. et sp. nov., two new species of the genus Raja, Raja amphitrita sp. nov. and Raja manitaria sp. nov., as well as remains of warm water adapted myliobatiforms. It is, however, not possible to unambiguously assign these remains either to Myliobatidae or Rhinopteridae, or to any specific genus. Previously reported remains of Raja/Bathyraja sp. are assigned to the new described species Raja manitaria sp. nov. The biogeographic distribution of extant and extinct rays and skates clearly shows that both groups are more widely distributed today than in the past, and additionally seem to have been more diverse in the Northern than the Southern Hemisphere. The occurrence, albeit rare of isolated teeth of skates (Rajidae) and rays (Myliobatidae) in the La Meseta Formation representes a minimum age constraint for their first appearance in the Southern Ocean.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:E507D86C-FFEC-4047-A337-AE77606BB1A6     

An intertidal balanomorph Hexaminius venerai sp. nov. (Austrobalanidae) colonizing a log of Podocarpoxylon from the La Meseta Formation (Eocene), Seymour Island,Antarctica: a glimpse of Antarctic antiquity

Abstract

The sessile barnacle Hexaminius venerai sp. nov. (Tetraclitoidea: Austrobalanidae) is described from the middle Eocene La Meseta Formation of Seymour Island, Antarctic Peninsula. Hexaminius venerai sp. nov. is the earliest known record of the genus in the Antarctic, the first occurrence of Hexaminius from outside Australian waters and the first record of a fossil cirripede attached to the substrate from the Antarctic. Exceptional preservation of more than 200 specimens, some of which retain opercula within the shell, is discussed. In life, the cirripedes were attached to a tree trunk tentatively identified as Podocarpoxylon, a South Hemisphere conifer. Hexaminius venerai sp. nov. is a survivor of an early phase in balanid radiation, prior to the development of strong radially-interlocked parietes.https://zoobank.org/urn:lsid:zoobank.org:pub:EAA2EB5C-BC57-41FA-93A0-046AF5FD59EB     

A new species of Dyrosaurus (Crocodylomorpha, Dyrosauridae) from the early Eocene of Morocco: phylogenetic implications

A new dyrosaurid is described from the Ypresian of the phosphatic deposits of the Oulad Abdoun Basin of Morocco. It is based on numerous cranial and postcranial remains, allowing an almost complete reconstruction. This new Dyrosaurus species, Dyrosaurus maghribensis sp. nov. , is currently only known from Morocco. It differs from D. phosphaticus , present in contemporaneous levels of Algeria and Tunisia, by several autapomorpies, including a smooth dorsal margin of the parietal and widely opened choanae. A phylogenetic analysis, using 47 taxa and 234 morphological characters, shows the dyrosaurids as the sister taxon of pholidosaurids, which include Elosuchus , Sarcosuchus , Terminonaris and Pholidosaurus , and the thalattosuchians. Goniopholididae is a non-monophyletic group; however, if dyrosaurids are not included in the analysis, the result differs and the goniopholidids form a distinct clade. If Thalattosuchia is excluded, both Goniopholididae and Pholidosauridae become paraphyletic assemblages. Thus, phylogenetic problems remain with respect to longirostrine clade, and more attention should be paid to resolving their evolutionary relationships amongst the crocodyliforms.  © 2006 The Linnean Society of London, Zoological Journal of the Linnean Society , 2006, 148 , 603–656.     

Intraspecific variation of Eolophiodon laboriense,a basal Lophiodontidae (Mammalia,Perissodactyla) from the early Eocene of Southern France

The Lophiodontidae is an emblematic and well-documented Eocene family of perissodactyls from Western Europe. However, after more than a century and a half of studies, lophiodontids still display a complex systematics associated with blurry intraspecific variation and a poorly known early radiation. The locality of La Borie, located near the city of Toulouse, France, has yielded numerous remains of Eolophiodon laboriense. This abundance of remains allows for the first time the study of the intraspecific variation of a basal lophiodontid. The variation has been investigated for dental and cranio-mandibular characters, notably dental polymorphism, size variation and sexual dimorphism. The intraspecific variation of E. laboriense is high with more than 20 polymorphic characters of the dentition, including many additional crests and conules. This dental polymorphism is similar to the one observed in the Bartonian lophiodontid Lophiodon lautricense. E. laboriense also displays an important degree of sexual dimorphism, with male specimens having broader and longer mandibles with larger canines than females. Despite this high intraspecific variation, the low size variation of teeth and the consistency of diagnostic characters strengthen the validity of the genus Eolophiodon and does not impact the previous lophiodontid phylogeny.     

Fossil penguin (Aves: Sphenisciformes) cranial material from the Eocene of Seymour Island (Antarctica)

Our knowledge of the cranial morphology of early penguins remains poor, particularly for Paleogene taxa. This paper describes a partial penguin skull and additional isolated cranial elements from the Eocene La Meseta Formation of Seymour Island, Antarctica. These specimens cannot be assigned to named taxa at present, but there is a strong possibility they belong to La Meseta penguins known only from postcranial elements. The skull shares extensive dorsal development of the temporal fossae with extant and fossil Spheniscus and the fossil penguins Paraptenodytes and Marplesornis, indicating the adductor complex was powerful in early penguins. Partial mandibles belonging to a much larger penguin are similar to Paraptenodytes and differ from all living penguins in the lack of a hooked medial process of the articular and the presence of a foramen anterior to the mandibular cotyles. Given the rarity of penguin cranial remains, these specimens provide important new insight into early penguin evolution.     

A new sawshark,Pristiophorus laevis,from the Eocene of Antarctica with comments on Pristiophorus lanceolatus

The highly fossiliferous Eocene deposits of the Antarctic Peninsula are among the most productive sites for fossil remains in the Southern Hemisphere and offer rare insights into high-latitude faunas during the Palaeogene. Chondrichthyans, which are represented by abundant isolated remains, seemingly dominate the marine assemblages. Eocene Antarctic sawsharks have only been known from few isolated rostral spines up to now, that were assigned to Pristiophorus lanceolatus. Here, we present the first oral teeth of a sawshark from the Eocene of Seymour Island and a re-evaluation of previously described Pristiophorus remains from Gondwana consisting exclusively of rostral spines. The holotype of Pristiophorus lanceolatus represents a single, abraded and insufficiently illustrated spine from the Oligocene of New Zealand. All other Cenozoic rostral spines assigned to this species are morphologically very indistinct and closely resemble those of living taxa. Consequently, we regard this species as dubious and introduce a new species, Pristiophorus laevis, based on oral teeth. The combination of dental characteristics of the new species makes it unique compared to all other described species based on oral teeth. Rostral spines from the Eocene of Seymour Island are assigned to this new species whereas those from other Cenozoic Gondwana localities remain ambiguous.

LSID urn:lsid:zoobank.org:pub:7177A373-527B-4315-85F6-25180DB5E087     

First fossilized skin of a giant penguin from the Eocene of Antarctica

An articulated wing belonging to Palaeeudyptes gunnari containing mineralized skin was found in Lutetian (middle Eocene) sediments from Seymour Island, Antarctica. It shows the connective tissues, morphology and density of the feather follicles, and a groove pattern left by the feather calami resting on the skin. Analysis of the preserved surfaces indicates a composition of calcium phosphate. This is the most complete and only articulated wing described for this species and represents the first record of a neornithine bird preserving three-dimensional integument. Plumage density of the wing MLP 14-I-10-22, estimated by counting the follicles under a stereoscopic microscope, is lower than that of the modern Emperor penguin.     

New material of Diacodexis (Mammalia,Artiodactyla) from the early Eocene of Southern Europe

Diacodexeidae are the first representatives of Artiodactyla in the fossil record. Their first occurrence is at the very base of the Ypresian (earliest Eocene, 56.0 Ma) with Diacodexis, a genus well diversified during the early Eocene in Europe, especially during the MP7–MP8 + 9 interval. However, most of European species are documented by scarce material, retrieved from single localities. In this work, we describe new Diacodexis material from ～MP7 and ～MP8 + 9 localities of Southern Europe, including material of D. antunesi from Silveirinha, considered as the most primitive European Diacodexis species, and material from three localities from Southern France (Fordones, Palette, and La Borie). The new material documents Diacodexis premolar morphology and deciduous dentition which bear potentially important phylogenetic information, as well as astragali, including a specimen from Silveirinha that constitutes the earliest occurrence of an astragalus of the genus Diacodexis in the European fossil record. Investigation of the enamel microstructure reveals that early European species had a simple enamel pattern with one-layered Schmelzmuster composed of ‘basic’ radial enamel only, instead of the two-layered Schmelzmuster (thin radial enamel + thick layer of Hunter-Schreger bands) observed on North American species and so far considered to represent the primitive condition within Artiodactyla. In accordance with previous studies, our observations highlight that Diacodexis gigasei from Belgium is morphologically closer to the North American species D. ilicis than to D. antunesi from Portugal. The latter species, together with D. aff. antunesi from Fordones, appears to be morphologically closer to the Asiatic taxa D. indicus and D. pakistanensis. Finally, we found numerous similarities between D. cf. gigasei from Palette and D. gigasei, a result that challenges the intra-European provincialism that characterizes the earliest Ypresian. Diacodexis gigasei could be one of the rare species shared by the northwestern and southwestern European bioprovinces.     

The Bryophytes of the King George Island,Antarctica

After examining the moss collections from the King George Island collected by Dr. Wei Jiang-chun and Mr. Li Zhen-pei in 1983–1984 and 1985 separately, we find 7 species of the mosses, which belong to 4 families and 6 genera. Some of them such as the mosses of Calliergon and Drepanocladus favour moist habitats, whereas Andreaea obovata indicates the dry rocky substratum. Barbula unguiculata and Tortula ruralis could suffer non-permanent dry condition. Geographically, except Andreaea obovata and Calliergon stramineum the other mosses are almost cosmopolitans. They probably distributed to the King George Island before Antarctica drifting to the recent position, and the strong wind was also possible to blow the spores of mosses to Antarctica.     

A New Decapod Trackway from the Upper Cretaceous, James Ross Island, Antarctica

A new trace fossil, Foersterichnus rossensis igen. nov. and isp. nov., is described from the Coniacian Hidden Lake Formation, James Ross Island, Antarctica. The trace fossil is a trackway comprising straight, or slightly curving, paired rows of elongate to tear-shaped impressions, parallel or slightly inclined to the long axis of the trackway. Foersterichnus is interpreted to be the trackway of a brachyuran decapod crustacean. It occurs in transgressive shallow marine deposits formed above the storm wave base in a shelf setting. Preservation of the trackway may have been linked to a rapid deoxygenation event during drowning that led to cessation of bioturbation allowing preservation of mixed layer trackways.     

The skeleton of early Eocene Cantius, oldest lemuriform primate

A recently discovered partial skeleton of the adapid Cantius trigonodus from the early Eocene Willwood Formation of the Bighorn Basin, Wyoming, documents substantial new information about the anatomy of the oldest lemuriform primates. It is very similar in all features to its descendant, middle Eocene Notharctus, and both exhibit numerous resemblances to certain extant Malagasy lemurs, particularly Lepilemur, Propithecus, Lemur, and Hapalemur griseus. Like these forms, Cantius had relatively long hind limbs and short forelimbs. Forelimb traits (prominent brachialis flange of the humerus, well-developed olecranon process of the ulna, and strong shafts of the ulna and radius) suggest active use of the forelimbs in progression. Specializations in the hind limb (e.g., expanded articular surface of the femoral head, narrow and elevated patellar trochlea and prominent lateral trochlear ridge, posteriorly oriented femoral and tibial condyles, narrow and elongate talus, and hallucal metatarsal with prominent peroneal tubercle) indicate capabilities for leaping and for powerful grasping with an opposable hallux. Cantius was presumably primitive in having a relatively long ischium and much more distal inferior tibial tuberosity than most extant lemurs--traits suggesting that powerful extension of the thigh and flexion at the knee were important in its locomotion and posture. We interpret Cantius as an active arboreal quadruped with a propensity for leaping. The existence of this skeletal structure in one of the oldest primates of modern aspect suggests that it represents the primitive lemuriform morphology.     

New remains of Egatochoerus jaegeri (Mammalia,Suoidea) from the late Eocene of Peninsular Thailand

Abstract: We report here additional remains referred to Egatochoerus jaegeri from the late Eocene locality of Ban Mark in the Krabi basin, Thailand. The new material described, comprising upper and lower cheek teeth, deciduous premolars and partial cranial remains, makes E. jaegeri the best‐documented Eocene representative of Old World Suoidea at present. Detailed study and comparison of their cheek teeth structure reveal a homogeneity of the molar crest and groove patterns of Old World and New World Palaeogene suoids.     

Additional vertebral material of Thaumastophis (Serpentes: Caenophidia) from the early Eocene of India provides new insights on the early diversification of colubroidean snakes

The Ypresian Cambay Shale Formation at Vastan, Mangrol, and Tadkeshwar lignite mines in Gujarat, western India, has yielded a rich vertebrate fauna including madtsoiid, palaeophiid, booid, and colubroidean-like snakes. The latter are particularly abundant, but their systematic affinities are difficult to resolve. Here we describe new specimens of the colubroidean-like snake Thaumastophis missiaeni, including anterior, middle, and posterior trunk vertebrae, as well as caudal vertebrae. The combination of primitive and derived caenophidian and colubroidean vertebral characters confirms Thaumastophis as the earliest known stem-colubriform snake while Procerophis, from the same beds, is more derived and considered to represent a crown-Colubriformes. Additionally, Thaumastophis shares with Renenutet enmerwer from the late Eocene of Egypt a unique combination of vertebral characters that suggests an exchange with North Africa was possible along the southern margin of the Neotethys. We erect the new family Thaumastophiidae for Thaumastophis and Renenutet on the basis of their shared derived vertebral morphology.     

Microbial mats of twenty-six lakes from Potter Peninsula,King George Island,Antarctica

The taxonomic composition and ecology of microbial mats were investigated in 26 lentic environments of Potter Peninsula (King George Island, Antarctica) during the summer of 1995/96. These have different limnological characteristics according to the location of the basins. Among the 139 algal taxa registered, 10 are new records for Antarctica. Bacillariophyceae was the dominant class in terms of species richness, followed by the Cyanobacteria and Chlorophyceae. TWINSPAN classification was used to describe six epilithic algal assemblages; Canonical Correspondence Analysis ordination showed that soluble reactive phosphorus, phytoplanktonic chlorophyll a concentration and conductivity were the main sources for the variation in the data.     

Diversity of the cyanobacterial microflora of the northern part of James Ross Island,NW Weddell Sea,Antarctica

The diversity and ecological distribution of cyanobacteria in the northern, deglaciated part of James Ross Island were studied during the Antarctic summer season 2005–2006. Seventy-five cyanobacterial morphotypes were observed in various habitats of this area. The identified cyanobacterial taxa belong to the characteristic and dominant types of coastal Antarctica, and majority of them appeared connected to special habitats and formed distinct populations and ecologically delimited communities. The results are compared and discussed with respect to phenotypically characterised cyanobacterial microflora of maritime Antarctica and to recent molecular analyses of cyanobacterial strains from different Antarctic regions. The existence of a specificity and characteristic composition of Antarctic cyanobacterial communities was demonstrated.     

Vertical distribution of macrobenthic infauna from the shallow sublittoral zone of Admiralty Bay,King George Island,Antarctica

A 0.0625 m² mini-box corer (MBC) was used to study the vertical distribution of macrobenthos in the shallow sublittoral zone of Admiralty Bay, during the 2003/2004 summer, near the Brazilian Station Comandante Ferraz, and the Peruvian Station Machu Picchu. Sediment samples were taken from 20, 30 and 60 m, and stratified for particle-size, total organic matter (TOM) and faunal composition analysis. The most abundant taxa were Polychaeta, Oligochaeta, Amphipoda, Cumacea, Bivalvia and Gastropoda. In general, macrofauna were concentrated in the 0–4 cm layer (64% of total organisms). Correlations between sediment characteristics and faunal densities have not completely explained neither the aggregation of organisms at the surface sediment layers nor the differences in faunal composition between locations at 20 m depth. Analysis of parameters such as organic carbon, heavy metals, interstitial water, and species composition should contribute to a better understanding of the diversity patterns found in this study.     

Systematics and diversity of the giant soft-shelled turtles (Cryptodira,Trionychidae) from the earliest Eocene of Belgium

In 1909, the famous paleontologist Louis Dollo identified two putative new species of giant soft-shelled turtles from the lowest Eocene record of Belgium, ‘Trionyx erquelinnensis’ and ‘Trionyx levalensis’, from Erquelinnes and Leval, respectively. However, these proposals did not meet the requirements of the International Code of Zoological Nomenclature, so they were considered as nomina nuda. The information on these specimens or about any other specimen of this lineage of giant turtles from the Belgian record is currently extremely limited. Relatively scarce material from giant trionychids has been described for the lower Eocene record of other European regions. Considering the available information, all the European material has recently been recognized as belonging to the genus Axestemys, which has a North American origin, and possibly attributable to a single species, Axestemys vittata, which currently lacks a diagnosis. Numerous and well-preserved Belgian specimens are deposited in the Royal Belgian Institute of Natural Sciences. In addition to the cited individuals from Erquelinnes and Leval, additional specimens from both localities, as well as others from Orp-le-Grand, are part of this collection. These specimens, found between the decades of 1910 and 1930, have been recently restored, and their study is carried out here. The presence of Axestemys vittata in Belgium (in Leval and Orp-le-Grand) is confirmed. Knowledge about this species is significantly improved, and a diagnosis is proposed. However, the hypothesis proposed by Dollo is here confirmed, this species being not the only identified in the Belgian record. So, Axestemys erquelinnensis nov. sp. is defined based on the carapace from Erquelinnes known by Dollo, suggesting that the genus probably reached Europe during the Paleocene Eocene Thermal Maximum.     

Limnological characteristics of the freshwater ecosystems of Byers Peninsula, Livingston Island, in maritime Antarctica

A limnological survey of 15 lakes and 6 streams was carried out on Byers Peninsula (Livingston Island, South Shetland Islands, Antarctica) during austral summer 2001–2002. Most of the surface waters had low conductivities (20–105 μS cm⁻¹) and nutrients (total phosphorus 0.01–0.24 μM), but some coastal lakes were enriched by nutrient inputs from seal colonies and marine inputs. Plankton communities in the lakes contained picocyanobacteria (10²–10⁴ cells ml⁻¹), diatoms, chrysophytes and chlorophytes, and a large fraction of the total biomass was bacterioplankton. Zooplankton communities were dominated by Boeckella poppei and Branchinecta gainii; the benthic cladoceran Macrothrix ciliata was also recorded, for the first time in Antarctica. The chironomids Belgica antarctica and Parochlus steinenii, and the oligochaete Lumbricillus sp., occurred in stream and lake benthos. The phytobenthos included cyanobacterial mats, epilithic diatoms and the aquatic moss Drepanocladus longifolius. These observations underscore the limnological richness of this seasonally ice-free region in maritime Antarctica and its value as a long-term reference site for monitoring environmental change.     

The influence of ice scour on benthic communities at three contrasting sites at Adelaide Island,Antarctica

Abstract Ice scouring is a key structuring force acting on high latitude shallow benthic communities. Despite its importance, detailed studies of scoured communities are still rare. Here we report the ecological effects of 12 iceberg impacts, across three contrasting study sites, at Adelaide Island, West Antarctic Peninsula. Grounded icebergs were marked with GPS and the newly formed scours (at 10–17 m depth) were sampled within 20 days of formation. Comparisons between scoured and adjacent unscoured assemblages were made using measures of abundance, biomass, taxon richness and the relative abundance of secondary consumers. Ice scouring was catastrophic at all sites, despite differences in substratum type, exposure and background community. Compared with undisturbed areas, scour assemblages were 95% lower in mean macrofaunal abundance and 75.9% lower in species richness. There was no general trend across all sites of ice scouring selecting for secondary consumers. The echinoid Sterechinus neumayeri and bivalve mollusc Mysella charcoti were highly abundant in undisturbed areas and were the biggest contributors to the observed differences between scours and undisturbed areas.