Mesozoic Diversity Research Articles

The Palaeozoic assembly of the holocephalan body plan far preceded post-Cretaceous radiations into the ocean depths.

Among cartilaginous fishes, Holocephali represents the species-depauperate, morphologically conservative sister to sharks, rays and skates and the last survivor of a once far greater Palaeozoic and Mesozoic diversity. Currently, holocephalan diversity is concentrated in deep-sea species, suggesting that this lineage might contain relictual diversity that now persists in the ocean depths. However, the relationships of living holocephalans to their extinct relatives and the timescale of their diversification remain unclear. Here, we reconstruct the evolutionary history of holocephalans using comprehensive morphological and DNA sequence datasets. Our results suggest that crown holocephalans entered and diversified in deep (below 1000 m) ocean waters after the Cretaceous-Palaeogene mass extinction, contrasting with the hypothesis that this ecosystem has acted as a refugium of ancient cartilaginous fishes. These invasions were decoupled from the evolution of key features of the holocephalan body plan, including crushing dentition, a single frontal clasper, and holostylic jaw suspension, during the Palaeozoic Era. However, these invasions considerably postdated the appearance of extant holocephalan families 150 million years ago during a major period of biotic turnover in oceans termed the Mesozoic Marine Revolution. These results clarify the origins of living holocephalans as the recent diversification of a single surviving clade among numerous Palaeozoic lineages.

The earliest fossil record of the extant rove beetle genus Phloeocharis from mid-Cretaceous Kachin amber of northern Myanmar and its biogeographic implications (Coleoptera: Staphylinidae: Phloeocharinae)

Phloeocharis Mannerheim is the largest genus within the problematic rove beetle subfamily Phloeocharinae, with a single extinct and 44 recent species recorded from the Holarctic region. Until now, the oldest fossil record of Phloeocharis was known from Late Cretaceous (Turonian) amber from New Jersey, USA. Here we describe †Phloeocharis burmana n. sp. from mid-Cretaceous (Albian–Cenomanian) Kachin amber from northern Myanmar, as the earliest extinct species of this genus. Our finding also sheds light on the biogeography of Phloeocharis, since no recent or extinct species have so far been recorded from the Oriental Region. Furthermore, the discovery of †P. burmana n. sp. extends the Mesozoic diversity of the phloeocharine rove beetles both taxonomically and morphologically, particularly from Kachin amber.

A new dragonfly genus and species from the Crato Formation, with a revised phylogenetic study of the Mesozoic family Liupanshaniidae (Odonata: Aeshnoptera)

The fourth genus and species of the Cretaceous aeshnopteran family Liupanshaniidae discovered in the Aptian Crato Formation, is described and illustrated as Brasiliupanshania cretacica gen. et sp. nov. Its phylogenetic position within the Liupanshaniidae is investigated using parsimony analyses, and it was found nested within the Liupanshaniidae. The Gondwanan species of the family do not form a clade, but appears to be more closely related to various Laurasian clades, suggesting a very ancient Mesozoic diversification prior to Gondwana–Laurasia split.

Evidence for Early Mesozoic diversification of Hypsimetopidae Nicholls, 1943 (Isopoda), with the description of a new genus from Andhra Pradesh and notes on threats to Indian cave environments

AbstractA new phreatoicidean isopod, Speonastes venkataramanigen., sp. nov. is described from Borra Cave in northeastern Andhra Pradesh, India. This new taxon has features seen in most phreatoicideans such as ventrally projecting pleonal pleurae, but also has features characteristic of the hypogean family Hypsimetopidae, such as an elongated pleotelson with a medially rotating uropod that has protopodal denticles or denticulate setae opposing the denticulate margin of the pleotelson, as well as the distal article of the antennula being minute and the penultimate article elongated and somewhat inflated. Robustness-tested phylogenetic analyses of character data from exemplars from nearly all phreatoicidean genera and four non-phreatoicidean outgroups finds that this species is the earliest derived member of Hypsimetopidae. These analyses have substantial implications for both relationships among Phreatoicidea, but within the family as well. The body form of the Phreatoicidea basal to the hypsimetopid clade resembles the form seen in fossils or by recent taxa such as CrenisopusWilson & Keable, 1999. Ancestors of Speonastesgen. nov. may have independently colonized India from those of the Nichollsia-Andhracoides clade. An early Mesozoic diversification of Hypsimetopidae and related taxa along continental rifts in eastern Gondwana between Antarctica, India, and Australia is one implication of the phylogeny. Although the caves of Andhra Pradesh and other Indian states have biologically unique and scientifically important taxa, India provides no protection for any cave. This exposes the fauna to negative impacts such as quarrying or illegal mining, over-exploitation of water resources, and damage from unconstrained tourist visitation.

A cranefly rendezvous: The highest known Mesozoic diversity of Tipulidae (Insecta: Diptera) in the Lower Cretaceous Crato Formation of NE Brazil

The genus Leptotarsus (Tipulomorpha: Tipulidae) is one of the oldest lineages of the family Tipulidae known from the Early Crataceous to the present. Most Leptotarsus fossils are from the Cretaceous period, and the Crato Formation of the Lower Cretaceous of NE Brazil is notable for bearing the greatest known Mesozoic diversity of the genus. This study describes twelve new species of the genus: Leptotarsus acciolii sp. nov., L. alemaoi sp. nov., L. bonifacioi sp. nov., L. capanemai sp. nov., L. coutoi sp. nov., L. feijoi sp. nov., L. ferreirai sp. nov., L. lagosi sp. nov., L. lemesi sp. nov., L. pereirai sp. nov., L. petrii sp. nov. and L. velosoi sp. nov. With the new taxa described herein, a total of 21 Leptotarsus species are now recorded from the Crato Formation. An updated identification key for all Cretaceous Leptotarsus species of the world is provided.

New mimarachnids (Hemiptera, Fulgoromorpha, Fulgoroidea) in mid-Cretaceous Burmese amber.

A new genus and species, Multistriaorthotropagen. et sp. nov., and a new species, Dachibangushuisp. nov., of Mimarachnidae are described from the mid-Cretaceous Burmese amber. These new taxa display unique wing color patterns and extend the Mesozoic diversity of Mimarachnidae. The evolution of wing venation, phylogenetic placement of Mimarachnidae, and anti-predation defenses of this family in Burmese amber forest are briefly discussed.

New Genera and Species of the Family Throscidae (Coleoptera: Elateroidea) in Mid-Cretaceous Burmese Amber.

Simple SummaryThroscidae is a relatively small lineage in the beetle superfamily Elateroidea. The Mesozoic fossil records of this family are sparse. Here we describe three new throscid species found in mid-Cretaceous Burmese amber, all represented by well-preserved specimens. These newly discovered species suggest that Throscidae had a high diversity in the Cretaceous.Captopus depressicepsgen. et sp. nov., Electrothroscus yanpingaegen. et sp. nov. and Pseudopactopus robustus gen. et sp. nov. are reported from the mid-Cretaceous Burmese amber. These new findings greatly extend the Mesozoic diversity of Throscidae, which implies a high degree of morphological disparity for this family in the Cretaceous.

A miniaturized ommatid beetle in mid-Cretaceous Burmese amber (Coleoptera: Archostemata: Ommatidae)

Recent findings of ommatids from mid-Cretaceous Burmese amber have greatly increased our knowledge on the Mesozoic diversity of Ommatidae. Here, we report the first distinctly miniaturized ommatid species, Miniomma chenkuni gen. et sp. nov., entombed in mid-Cretaceous amber from northern Myanmar. This new fossil species is characterized by its small body size (less than 2 mm long) and subglobular metacoxae. Our discovery of miniaturization in extinct Ommatidae suggests a high ecological diversity of this family in the Mesozoic.

A one-billion-year-old multicellular chlorophyte.

Chlorophytes (which represent a clade within the Viridiplantae and a sister group of the Streptophyta) probably dominated marine export bioproductivity and played a key role in facilitating ecosystem complexity before the Mesozoic diversification of phototrophic eukaryotes such as diatoms, coccolithophorans, and dinoflagellates. Molecular clock and biomarker data indicate that chlorophytes diverged in the Mesoproterozoic or early Neoproterozoic, followed by their subsequent phylogenetic diversification, multicellular evolution, and ecological expansion in the late Neoproterozoic and Paleozoic. This model, however, has not been rigorously tested with paleontological data because of the scarcity of Proterozoic chlorophyte fossils. Here we report abundant millimeter-sized, multicellular, and morphologically differentiated macrofossils from ~1,000 Ma rocks. These fossils are described as Proterocladus antiquus new species and are interpreted as benthic siphonocladalean chlorophytes, suggesting that chlorophytes acquired macroscopic size, multicellularity, and cellular differentiation nearly a billion years ago, much earlier than previously thought.

The evolution and genomic basis of beetle diversity

The order Coleoptera (beetles) is arguably the most speciose group of animals, but the evolutionary history of beetles, including the impacts of plant feeding (herbivory) on beetle diversification, remain poorly understood. We inferred the phylogeny of beetles using 4,818 genes for 146 species, estimated timing and rates of beetle diversification using 89 genes for 521 species representing all major lineages and traced the evolution of beetle genes enabling symbiont-independent digestion of lignocellulose using 154 genomes or transcriptomes. Phylogenomic analyses of these uniquely comprehensive datasets resolved previously controversial beetle relationships, dated the origin of Coleoptera to the Carboniferous, and supported the codiversification of beetles and angiosperms. Moreover, plant cell wall-degrading enzymes (PCWDEs) obtained from bacteria and fungi via horizontal gene transfers may have been key to the Mesozoic diversification of herbivorous beetles-remarkably, both major independent origins of specialized herbivory in beetles coincide with the first appearances of an arsenal of PCWDEs encoded in their genomes. Furthermore, corresponding (Jurassic) diversification rate increases suggest that these novel genes triggered adaptive radiations that resulted in nearly half of all living beetle species. We propose that PCWDEs enabled efficient digestion of plant tissues, including lignocellulose in cell walls, facilitating the evolution of uniquely specialized plant-feeding habits, such as leaf mining and stem and wood boring. Beetle diversity thus appears to have resulted from multiple factors, including low extinction rates over a long evolutionary history, codiversification with angiosperms, and adaptive radiations of specialized herbivorous beetles following convergent horizontal transfers of microbial genes encoding PCWDEs.

New occurrences of fossil Testudines of the Romualdo Formation, Aptian-Albian of the Araripe Basin, Pernambuco, Northeast Brazil

So far, there are at least 22 species of fossil turtles formally described for Brazil, with the Araripe Basin being the second largest in Mesozoic diversity with five species, losing only to the Bauru Group, with six species. The material presented here refers to three fossil turtles (DGEO-CTG-UFPE 8470, DGEO-CTG-UFPE 8471, DGEO-CTG-UFPE 8932) from Romualdo, an Albian Formation of the Araripe Basin (Cretaceous), collected in municipalities of Pernambuco (PE). The DGEO-CTG-UFPE 8470 specimen was identified as Araripemys barretoi Price, 1973, and DGEO-CTG-UFPE 8471 and DGEO-CTG-UFPE 8932 as Cearachelys placidoi Gaffney et al., 2001, the first occurrence of this taxon in the state of Pernambuco. DGEO-CTG-UFPE 8470 and DGEO-CTG-UFPE 8932 are the first Testudines described from the municipality of Exu, (PE).

Evidence from Australian mesic zone dung beetles supports their Gondwanan origin and Mesozoic diversification of the Scarabaeinae

The evolution of dung beetles remains contentious with two hypotheses reflecting Cretaceous and Paleogene origins driven by different methods. We explore biogeographic evidence and phylogeographic origins against vicariance and dispersal scenarios that attribute to the four elements of the Australian fauna using a multi-gene approach. Maximum-likelihood and Bayesian analyses supported the Australasian clade, composed of almost all Australian, New Caledonian and New Zealand endemic genera (to the exclusion of Boletoscapter). Two Australian lineages with east-west splits and few lineages with restricted, non-overlapping distrbution were identified, and biogeography models provided evidence that vicariance and founder event speciation are important processes in the diversification of Australasian scarabaeines. Our phylogenetic results are largely congruent with a mid-Cretaceous origin of the Australasian clade, the tectonic history of Gondwanaland and climatic history of the Australian continent, and provide compelling evidence that Australian dung beetles are a relictual fauna whose history is linked to mesic zone fragmentation.

Near-Stasis in the Long-Term Diversification of Mesozoic Tetrapods.

How did evolution generate the extraordinary diversity of vertebrates on land? Zero species are known prior to ~380 million years ago, and more than 30,000 are present today. An expansionist model suggests this was achieved by large and unbounded increases, leading to substantially greater diversity in the present than at any time in the geological past. This model contrasts starkly with empirical support for constrained diversification in marine animals, suggesting different macroevolutionary processes on land and in the sea. We quantify patterns of vertebrate standing diversity on land during the Mesozoic–early Paleogene interval, applying sample-standardization to a global fossil dataset containing 27,260 occurrences of 4,898 non-marine tetrapod species. Our results show a highly stable pattern of Mesozoic tetrapod diversity at regional and local levels, underpinned by a weakly positive, but near-zero, long-term net diversification rate over 190 million years. Species diversity of non-flying terrestrial tetrapods less than doubled over this interval, despite the origins of exceptionally diverse extant groups within mammals, squamates, amphibians, and dinosaurs. Therefore, although speciose groups of modern tetrapods have Mesozoic origins, rates of Mesozoic diversification inferred from the fossil record are slow compared to those inferred from molecular phylogenies. If high speciation rates did occur in the Mesozoic, then they seem to have been balanced by extinctions among older clades. An apparent 4-fold expansion of species richness after the Cretaceous/Paleogene (K/Pg) boundary deserves further examination in light of potential taxonomic biases, but is consistent with the hypothesis that global environmental disturbances such as mass extinction events can rapidly adjust limits to diversity by restructuring ecosystems, and suggests that the gradualistic evolutionary diversification of tetrapods was punctuated by brief but dramatic episodes of radiation.

A Cretaceous Cusk-Eel (Teleostei, Ophidiiformes) from Italy and the Mesozoic Diversification of Percomorph Fishes

Cusk-eels of the order Ophidiiformes are a morphologically diverse assemblage of eel-like, elongate, posteriorly tapering percomorph fishes that occur worldwide in marine waters, from tropical reef areas to the deep sea. The about 400 extant and fossil species included in the ophidiiform clade are arranged into two main lineages, Bythitoidei and Ophidioidei, based on reproductive biology and the position of the anterior nostrils. The anatomy and phylogenetic relationships of these fishes are largely unknown, and the fossil record has not provided substantial information about the earliest phases of their evolutionary history. †Pastorius methenyi, new genus and species, the oldest member of the Ophidiiformes based on articulated skeletal remains, is described herein based on a single specimen collected from the Campanian-Maastrichtian organic-rich laminated limestone of the Liburnica Formation outcropping near the village of Trebiciano, north-eastern Italy. The comparative analysis of osteological and meri...

Mesozoic Diversity of Osmundaceae: Osmundacaulis whittlesii sp. nov. in the Early Cretaceous of Western Canada

Premise of research. A distinctive new species of osmundaceous fern, based on a permineralized trunk from Lower Cretaceous deposits of Haida Gwaii (formerly the Queen Charlotte Islands) off the west coast of mainland Canada, provides additional data for addressing the Mesozoic diversity and the overall pattern of phylogeny for osmundaceous filicalean ferns.Methodology. The specimen was cut into segments and studied from both external morphology and anatomical sections prepared by the cellulose acetate peel technique. Microscope slides of sections were examined, and images were captured under transmitted light.Pivotal results. The fossil represents a new species of Osmundacaulis, which is only the third Northern Hemisphere representative of this predominantly Southern Hemisphere genus.Conclusions. Osmundacaulis whittlesii sp. nov. increases the Northern Hemisphere diversity of Cretaceous Osmundaceae, thus providing new data about Mesozoic diversity of the clade, potential sister-group relationships of crown-group Osmundaceae, and the overall pattern of phylogeny for Osmundaceae.

OMANASTER IMBRICATUS (ECHINODERMATA, ASTEROIDEA), A NEW GENUS AND SPECIES FROM THE SAKMARIAN (LOWER PERMIAN) SAIWAN FORMATION OF OMAN, ARABIAN PENINSULA

Omanaster imbricatus is a new genu s and species of Sakmarian (Early Permian) asteroids collected from the basal Pachycyrtella Bed of the Saiwan Formation of Oman, Arabian Peninsula; the family Omanasteridae is recognized. Late Paleozoic and especially Permian asteroids are rare and O. imbricatus differs significantly from those previously described, thereby providing an important addition to known late Paleozoic diversity. Unfortunately the single available specimen is incomplete with remaining ossicles both leached and partially fused, and available data are limited. Adambulacral form and arrangement of O. imbricatus are both suggestive of corresponding expressions of certain earlier Paleozoic species and unlike those of the crown-group, suggesting an enduring Paleozoic lineage but one not phylogenetically a part of the Mesozoic diversification. The Pachycyrtella Bed has been interpreted as recording a succession of pioneer palaeocommunities colonizing a turbulent, shallow-water settingaffected by oscillatory flows. The apparently flattened appearance of O. imbricatus is suggestive of appearances of certain Cretaceous and extant species recovered from similar environments thus suggesting both homoplasy and the versatility of asteroid evolution across extended spans of geologic time.

Anurans from the Early Cretaceous Lagerstätte of Las Hoyas, Spain: New evidence on the Mesozoic diversification of crown-clade Anura

The late Barremian laminated limestones of Las Hoyas in eastern Spain are famous for the large number, diversity, and quality of the fossils that they have yielded. Herein, anuran remains from these beds representing two new taxa are thoroughly described. Iberobatrachus angelae gen. et sp. nov. is characterized by a skull nearly as long as it is wide, a narrow neurocranium, frontoparietals fused at least along the posterior half of the orbital length, a distinct palatine process on maxilla, and moderately expanded sacral diapophyses. In turn, Gracilibatrachus avallei gen. et sp. nov. is characterized by a combination of characters that includes an azygous frontoparietal, eight presacral vertebrae, a monovertebral sacrum bearing narrow diapophyses, a bicondylar sacro-urostylar articulation, highly elongate metacarpals, and long distal manual phalanges. The anatomical evidence retrieved in this study is used to explore the taxonomic positions of the new taxa through a maximum parsimony analysis. This analysis supports the placement of I. angelae within Costata close to the extant genus Discoglossus, whereas G. avallei is nested within Xenoanura, as a basal pipimorph. These records corroborate that diversification of costatan and xenoanuran “archaeobatrachian” lineages were already well underway by the Early Cretaceous.

New gomphaeschnids and progobiaeshnids from the Yixian Formation in Liaoning Province (China) illustrate the tremendous Upper Mesozoic diversity of the aeshnopteran dragonflies

One new genus and five new species of dragonflies (Odonata) are described and figured from the Yixian Formation of northeastern China, viz. two gomphaeschnids Sinojoria magna nov. sp. and S. cancellosa nov. sp., plus three progobiaeshnids Mongoliaeshna hadrens nov. sp., M. exiguusens nov. sp., and Decoraeshna preciosus nov. gen., nov. sp. These new discoveries confirm the apparently sudden great diversification in China of the clade Aeshnoptera during the Middle-Upper Jurassic, together with the Upper Mesozoic to modern lineages of dragonflies. At the same time, some ‘ancient’ groups of Odonata became extinct.

Predator-induced macroevolutionary trends in Mesozoic crinoids

Sea urchins are a major component of recent marine communities where they exert a key role as grazers and benthic predators. However, their impact on past marine organisms, such as crinoids, is hard to infer in the fossil record. Analysis of bite mark frequencies on crinoid columnals and comprehensive genus-level diversity data provide unique insights into the importance of sea urchin predation through geologic time. These data show that over the Mesozoic, predation intensity on crinoids, as measured by bite mark frequencies on columnals, changed in step with diversity of sea urchins. Moreover, Mesozoic diversity changes in the predatory sea urchins show a positive correlation with diversity of motile crinoids and a negative correlation with diversity of sessile crinoids, consistent with a crinoid motility representing an effective escape strategy. We contend that the Mesozoic diversity history of crinoids likely represents a macroevolutionary response to changes in sea urchin predation pressure and that it may have set the stage for the recent pattern of crinoid diversity in which motile forms greatly predominate and sessile forms are restricted to deep-water refugia.

The cranial morphology of a new genus of lungfish (Osteichthyes: Dipnoi) from the Upper Jurassic Morrison Formation of North America

ABSTRACT Much of Mesozoic diversity within the lungfishes (Osteichthyes: Dipnoi) has traditionally been relegated to the genus Ceratodus, primarily on the basis of the highly stereotypical dental plates characteristic of post-Devonian lungfishes. The new genus Potamoceratodus contains the single species P. guentheri (Marsh, 1878), comb. nov. Newly discovered material allows clarification of the features of this species, including description of a complete skull roof and partial palate. The new genus can be differentiated from the European Ceratodus on the basis of characters of the skull roof, palate, and dentition, including lack of tubercular ornamentation of the skull roof, modest convexity of the dorsal skull roof, absence of sensory sulci anteriorly in the EF bone, and an enlarged and elongate anterior odontode series on the pterygoid dental plate. The North American Ceratodus record is reexamined in light of more complete material from the Temple Canyon localities of the Morrison Formation of Colorado, USA. Ceratodus is found to be an assemblage of forms with disparate cranial morphology. The succession of North American lungfish communities in the late Paleozoic and Mesozoic is most characteristic of serial replacement rather than in situ evolution, and it is possible that the isolation of North America subsequent to the breakup of Laurentia contributed to the regional extinction of lungfishes in North America.