Scarce Fossil Record Research Articles

Lower Ordovician synziphosurine reveals early euchelicerate diversity and evolution

Euchelicerata is a clade of arthropods comprising horseshoe crabs, scorpions, spiders, mites and ticks, as well as the extinct eurypterids (sea scorpions) and chasmataspidids. The understanding of the ground plans and relationships between these crown-group euchelicerates has benefited from the discovery of numerous fossils. However, little is known regarding the origin and early evolution of the euchelicerate body plan because the relationships between their Cambrian sister taxa and synziphosurines, a group of Silurian to Carboniferous stem euchelicerates with chelicerae and an unfused opisthosoma, remain poorly understood owing to the scarce fossil record of appendages. Here we describe a synziphosurine from the Lower Ordovician (ca. 478 Ma) Fezouata Shale of Morocco. This species possesses five biramous appendages with stenopodous exopods bearing setae in the prosoma and a fully expressed first tergite in the opisthosoma illuminating the ancestral anatomy of the group. Phylogenetic analyses recover this fossil as a member of the stem euchelicerate family Offacolidae, which is characterized by biramous prosomal appendages. Moreover, it also shares anatomical features with the Cambrian euarthropod Habelia optata, filling the anatomical gap between euchelicerates and Cambrian stem taxa, while also contributing to our understanding of the evolution of euchelicerate uniramous prosomal appendages and tagmosis.

Modeling the mosaic structure of bacterial genomes to infer their evolutionary history

The chronology and phylogeny of bacterial evolution are difficult to reconstruct due to a scarce fossil record. The analysis of bacterial genomes remains challenging because of large sequence divergence, the plasticity of bacterial genomes due to frequent gene loss, horizontal gene transfer, and differences in selective pressure from one locus to another. Therefore, taking advantage of the rich and rapidly accumulating genomic data requires accurate modeling of genome evolution. An important technical consideration is that loci with high effective mutation rates may diverge beyond the detection limit of the alignment algorithms used, biasing the genome-wide divergence estimates toward smaller divergences. In this article, we propose a novel method to gain insight into bacterial evolution based on statistical properties of genome comparisons. We find that the length distribution of sequence matches is shaped by the effective mutation rates of different loci, by the horizontal transfers, and by the aligner sensitivity. Based on these inputs, we build a model and show that it accounts for the empirically observed distributions, taking the Enterobacteriaceae family as an example. Our method allows to distinguish segments of vertical and horizontal origins and to estimate the time divergence and exchange rate between any pair of taxa from genome-wide alignments. Based on the estimated time divergences, we construct a time-calibrated phylogenetic tree to demonstrate the accuracy of the method.

Kekveus brevisulcatus sp. nov., a new featherwing beetle from mid-Cretaceous amber of northern Myanmar (Coleoptera: Ptiliidae).

Ptiliidae (featherwing beetles) is a group of minute staphylinoid beetles with a scarce fossil record. Here a second member of the Mesozoic genus Kekveus Yamamoto et al. is reported from mid-Cretaceous Burmese amber, with detailed morphology obtained through confocal microscopy. Kekveus brevisulcatus Li, Yamamoto, Newton & Cai sp. nov. shares with K. jason Yamamoto et al. the unpaired medial pronotal fovea and narrowly separated transverse metacoxae, but can be separated from the latter based on its less elongate body, shorter pronotal foveae, and much weaker transverse depression on the head. Our phylogenetic analyses support the discheramocephalin affinity of Kekveus, although its relationship with other members of Discheramocephalini cannot be confidently resolved.

First afrosoricid out of Africa: an example of Pliocene ‘tourism’ in Europe

The afrosoricids are an endemic order exclusively from Africa with a very scarce fossil record. In this work, we present the first record outside this continent. The “otter shrew” Europotamogale melkarti n. gen. n. sp. was found in the Moreda 3 karstic fill site in Granada (Spain), of MN15 age (mid-Pliocene). This new taxon confirms the semiaquatic faunal interchange between Europe and Africa. We hypothesize that this tenrecid, representative of a family frequently present in the Central African faunas, migrated to the north of the continent via the Sahabi river system that connected North and Central Africa. Europotamogale n. gen. is the first known afrosoricid that migrated between the two continents. It was present in Europe for a very short time (as a ‘tourist genus’). To date, this phenomenon has only been described in genera of European origin, such as the pika Prolagus or the mouse Apodemus.

A new large tortoise from the early Oligocene (Arikareean NALMA) of Oaxaca, southern Mexico and its phylogenetic position within Pan-Testudinidae

ABSTRACT Pan-Testudinidae is the total clade of extant terrestrial tortoises, which includes extinct fossil members of their stem lineage. Members of this clade have a rather scarce fossil record in Mexico, and the few specimens known in scientific collections are poorly studied. Here, we described a new species of basal testudinid turtle, based on a single specimen from the early Oligocene deposits exposed in the marginal facies of the Chilapa Formation in Oaxaca, southern Mexico. The new taxon exhibits osteological characteristics that support its insertion as a basal Testudinidae. The phylogenetic relationships of the new turtle were assessed using a total evidence approach (morphological + molecular) in a global Pan-Testudinidae context using Implied Weighted Maximum Parsimony (IWMP), Standard Maximum Parsimony (SMP) and Bayesian Inference (BI). Although the BI consensus tree is not well resolved, the results obtained by IWMP and SMP retrieved its branching close to the root of Testudinidae. The differences between the topologies of the three phylogenetic analyses show that the position of several taxa within Testudinidae is affected by the phylogenetic analyses performed. The new taxon from Oaxaca, here reported, represents the first Palaeogene and the southernmost tortoise described from Mexico and the oldest Testudinidae known in the country.

The reevaluation of Salacia lombardii (Celastraceae) based on phylogenetic position and biogeographic implications

Biological inclusions preserved in the amber deposits from Chiapas, Mexico, provide evidence of a tropical environment at low latitudes in North America during the Miocene. Unfortunately, they have a scarce fossil record of plants, and most of them have been related to the extant taxa of the Neotropical region. However, this idea has not been evaluated through a phylogenetic context until now. Here, we analyzed the phylogenetic position of Salacia lombardii, a Miocene flower identified as an extinct species of Salacioideae (Celastraceae), which typically has flowers with a pentamerous perianth and trimerous androecium; nevertheless, a small set of taxa including S. lombardii have only two stamens. To evaluate the relationship between fossils with their potential near relatives, we used a combined matrix previously generated with molecular data combined with morphological characters from 6 genera and 28 species of Salacioideae through Parsimony and Bayesian criteria. The topologies of trees reported here are consistent with previous analyses for Salacioideae, recovering two clades: Neotropical and taxa with two-stamens. Salacia lombardii has an ambiguous position causing a polytomy in the strict consensus of Parsimony analysis. Nevertheless, there are only two alternative positions of the fossil in the MPTs (Most Parsimonious Trees): 1) as a sister group of Salacioideae or 2) as the sister group of clade from which Sarawakodendron and Salacioideae diverged. The latter is comparable with the tree of Bayesian analysis. Based on the criterion of topological congruence between Parsimony and Bayesian approaches, we support the second hypothesis, which suggests that Salacia lombardii occupies a transitional position between Salacioideae and Hippocrateoideae, as well as its close relationship with the Paleotropical region.

The oldest fossil of the sawfly subfamily Nematinae (Hymenoptera: Tenthredinidae) from the Paleocene of Menat (France)

The speciose family Tenthredinidae has a scarce fossil record (Nel et al., 2022a, b), despite recent molecular-based phylogenetic analyses suggesting a Cretaceous age for the origin (ca. 100 Ma) and the diversification of the family into its modern subfamilies (Nyman et al., 2006, 2019; Niu et al., 2021). The lack of Mesozoic representative of this group remains unexplained because Nyman et al. (2006) dated its origin at 100 Ma. Cenozoic fossils are currently attributed to the subfamilies Allantinae, Heterarthrinae, Blennocampinae, and Nematinae (Taeger et al., 2010; Nel et al, 2022a, b).

The First Fossil of Nossidiinae From Mid-Cretaceous Amber of Northern Myanmar (Coleoptera: Ptiliidae)

Ptiliidae is a group of distinctly miniaturized staphylinoid beetles with a scarce fossil record. Here, we report a new ptiliid genus and species, Crenossidium slipinskii Li, Newton and Cai gen. et sp. nov., from mid-Cretaceous amber from northern Myanmar. Crenossidium can be attributed to the subfamily Nossidiinae based on the hind wing morphology, which has also been confirmed through phylogenetic analyses. Crenossidium differs from other extant nossidiine genera in the combination of the wide apical maxillary palpomeres, posteriorly widest pronotal disk, (almost) contiguous procoxae, fewer setae along wing margin, and multidentate pygidium.urn:lsid:zoobank.org:pub:8038D763-6856-4AC5-972C-E20D636137EE.

A new look at the Cretaceous Lamprey Mesomyzon Chang, Zhang & Miao, 2006 from the Jehol Biota

Lampreys, one of the remaining two living jawless vertebrates, carry great weight in the study of vertebrate evolution. They have a long history dating back to the Devonian but left a scarce fossil record. So far, only five unequivocal fossil lampreys have been described, of which four are Paleozoic. Mesomyzon Chang, Zhang & Miao, 2006, the only known Mesozoic lamprey bridging the Paleozoic and extant relatives, was originally considered similar in morphology and life history to modern forms. Although being repeatedly referred to in early vertebrate phylogeny, the morphology of Mesomyzon is far from adequately known. Based on extensive investigations on numerous new and well-preserved specimens, we present herein more details of the morphology of this fossil lamprey, thereby releasing a package of new information of the cranial nerves, some associated structures of the oral disc, and the naso-hypophysial complex, which are barely preserved in previously known fossil lampreys. Mesomyzon shows peculiarities in having an extremely long anterior dorsal fin and a ribbon-like preanal skin fold, and hence being restored in a distinct profile from the formerly claimed look. Additionally, it shares with some Southern Hemispheric species the widely separated dorsal fins, posteriorly positioned cloaca and enlarged oral papillae. In the light of these new data, the feeding ecology of Mesomyzon was tentatively discussed and this fossil lamprey was considered a likely blood feeder, judging from the reinforcement of the attachment and sensory structures on the periphery of the oral disc.

An assemblage of giant aquatic snakes (Serpentes, Palaeophiidae) from the Eocene of Togo

We here describe a monospecific assemblage of giant aquatic snakes from the middle Eocene of Kpogamé, Togo. The material, consisting of large isolated vertebrae, is referred to Palaeophis africanus, an enigmatic palaeophiid species, which was so far otherwise known only from a limited number of vertebrae from the middle Eocene of Nigeria and Angola. Material from the late Eocene of the eastern USA that had been referred to the same species, is here instead considered too fragmentary for species-level determination and Palaeophis africanus is thus so far restricted to Africa. With the aid of micro-CT scanning, we present 3D models of 17 vertebrae, pertaining to different portions of the vertebral column. We provide detailed comparisons of the new material with all named African species of the genus Palaeophis. A tentative diagnosis of Palaeophis africanus is provided. With more than 50 vertebrae, the new Togolese specimens represent the most abundant known material attributed to Palaeophis africanus and significantly enhance our knowledge of the vertebral anatomy and intracolumnar variation for this taxon. Furthermore, this adds to the, as yet, extremely scarce fossil record of squamates from central western Africa, a region where Paleogene herpetofaunas are only rather poorly known.

Debris-carrying behaviour of bark lice immatures preserved in 100 million years old amber

Camouflage strategies, including several types of concealments, are known for several insect groups today, such as immatures of some species within reduviid bugs (Hemiptera), lace wings (Neuroptera), caddisflies (Trichoptera) and bark lice (Psocodea). However, camouflage has only rarely been reported in the fossil record. Here we report findings of four bark lice preserved in 100 Million year old amber from Myanmar, which represent the first fossil evidence for masking behaviour in Cretaceous representatives of Psocodea. All four of these, probably not conspecific, and immature bark lice carry sand granules and organic material atop their back, which probably resulted in camouflaging them against the background (e.g. bark) to avoid detection by predators. We briefly summarise concepts of camouflage and examples of decoration behaviour within insects, as well as possible “receiver” (i.e. predators) of the camouflage of the herein described bark lice. The exact phylogenetic position of the specimens remains unclear, due to the scarce fossil record of Cretaceous immatures of Psocodea, as well as extant immatures. This demonstrates the importance of findings as reported here, as a wide knowledge of morphology and development of a certain group is crucial to get an insight into their evolution and reconstructing environments in deep time.

Contrasting genetic signal of recolonization after rainforest fragmentation in African trees with different dispersal abilities

Although today the forest cover is continuous in Central Africa, this may have not always been the case, as the scarce fossil record in this region suggests that arid conditions might have significantly reduced tree density during the ice ages. Our aim was to investigate whether the dry ice age periods left a genetic signature on tree species that can be used to infer the date of the past fragmentation of the rainforest. We sequenced reduced representation libraries of 182 samples representing five widespread legume trees and seven outgroups. Phylogenetic analyses identified an early divergent lineage for all species in West Africa (Upper Guinea) and two clades in Central Africa: Lower Guinea-North and Lower Guinea-South. As the structure separating the Northern and Southern clades-congruent across species-cannot be explained by geographic barriers, we tested other hypotheses with demographic model testing using δαδι. The best estimates indicate that the two clades split between the Upper Pliocene and the Pleistocene, a date compatible with forest fragmentation driven by ice age climatic oscillations. Furthermore, we found remarkably older split dates for the shade-tolerant tree species with nonassisted seed dispersal than for light-demanding species with long-distance wind-dispersed seeds. Different recolonization abilities after recurrent cycles of forest fragmentation seem to explain why species with long-distance dispersal show more recent genetic admixture between the two clades than species with limited seed dispersal. Despite their old history, our results depict the African rainforests as a dynamic biome where tree species have expanded relatively recently after the last glaciation.

A new enigmatic lineage of Dascillidae (Coleoptera: Elateriformia) from Eocene Baltic amber described using X-ray microtomography, with notes on Karumiinae morphology and classification

Abstract. Dascillidae are a species-poor beetle group with a scarce fossil record. Here, we describe Baltodascillus serraticornis gen. et sp. nov. based on a well-preserved specimen from Eocene Baltic amber. It differs from all known Dascillidae by its reduced mandibles. After studying the specimen using light microscopy and X-ray microtomography, we tentatively place this genus in the poorly defined subfamily Karumiinae based on the large eyes, serrate antennae, and lack of prosternal process. This is the first representative of the Dascillidae formally described from Baltic amber and the first described fossil member of the subfamily Karumiinae. We briefly discuss the problematic higher classification of Dascillidae, along with the morphology and biogeography of the group.

A Review of the Fossil Record of Afro-Arabian Turtles of the Clade Testudinoidea

Turtles of the clade Testudinoidea have a rather scarce fossil record in Afro-Arabia, ranging from the late Eocene up to the Quaternary. The vast majority of testudinoid fossils from Afro-Arabia are ascribed to Testudinidae, which has had a continuous presence in the area since the late Eocene. Geoemydidae is poorly documented by fragments found throughout the Neogene across northern Africa and the Middle East. Emydidae is absent from the fossil record of this area. All valid named taxa pertain to testudinids. Within Testudinidae, the majority of known fossil species are members of the clade Geochelona, while a few others belong to the clade Testudona. Four fossil taxa are members of now-extinct genera, five are members of extant genera, and seven cannot be assigned to a known genus with certainty. The fossil record also documents that several extant genera had a much broader distribution during the Neogene and Quaternary. Endemic insular lineages were formerly present on the Canary Islands, Cape Verde islands, and on several islands in the Western Indian Ocean. The highest known diversity of testudinoids seems to have existed during the Neogene; however, definitive conclusions are hampered by the extremely poor Paleogene record and large, unsampled areas of Afro-Arabia. A taxonomic review of the 22 named Afro-Arabian taxa finds 16 nomina valida, 1 nomen invalidum, and 5 nomina dubia.

FIRST REVIEW OF THE LYNCODONTINI MATERIAL (MUSTELIDAE, CARNIVORA, MAMMALIA) FROM THE LOWER PLEISTOCENE ARCHAEO-PALAEONTOLOGICAL SITES OF ORCE (SOUTHEASTERN SPAIN)

Two archaeo-palaeontological Lower Pleistocene sites of Orce (Baza Basin, SE Spain), Fuente Nueva 3 (1.3 Ma) and Barranco Leon (1.4 Ma), preserve some of the earliest evidences of human presence in the European continent. During the 2013 field season, a small Lyncodontini mustelid mandible was found at Fuente Nueva-3. This finding was accompanied by a lower canine (c1), also from the same site, and a lower fourth premolar (p4) from Barranco Leon. Here, we report on the morphological and biometrical study of these materials, in comparison to other Eurasian Pliocene-Pleistocene species of the tribe Lyncodontini. The analyses revealed an affinity between the taxon from Fuente Nueva-3 and Barranco Leon with the small-sized European species Martellictis ardea (Gervais, 1848-1852), allowing us to ascribe the described material to the latter species. The presence of M. ardea in the sites of Orce is the southernmost occurrence of the species in the Iberian Peninsula and an important finding in the scarce fossil record of Lyncodontini in Europe.

A new species ofAmpulicomorphaAshmead from Eocene French amber, with a list of fossil and extant Embolemidae (Insecta: Hymenoptera) of the world

Embolemidae is a cosmopolitan but species-poor group of chrysidoid wasps with a scarce fossil record, despite a long evolutionary history since at least the Early Cretaceous. Here, the new species,Ampulicomorpha quesnoyensissp. nov., is illustrated and described based on a single female found in Early Eocene amber of Oise (France). The new species is compared with the three other known fossil species of the genus, and a key to all fossil species ofAmpulicomorphais provided. This is the third European fossil species ofAmpulicomorpha, which suggests that the genus was once well established in Western Europe while it is more widely distributed in the Eastern Palaearctic region today. A list of all fossil and extant Embolemidae of the world, as well as a map of their geographical distribution map, are provided.

Tracing insular woodiness in giant Daucus (s.l.) fruit fossils from the Early Pleistocene of Madeira Island (Portugal)

AbstractPlants on oceanic islands can evolve insular syndromes such as secondary woodiness, a generalized trend found in island floras worldwide. This phenomenon occurs through evolution in situ. It is triggered by ecological and physiological stimuli that transform herbaceous annuals into woody perennials. However, well‐dated and informative fossils that could help track and frame the evolution of this syndrome are lacking. Remarkably, in Madeira Island (Portugal), there are good examples of Apiaceae that evolved secondary woodiness, like the giant neoendemic Melanoselinum (≡ Daucus). Apiaceae has a very scarce fossil record, despite being a cosmopolitan family and an economically important crop. Here we describe the oldest Daucus s.l. fossil known to date and the first fossil evidence of a plant with insular woodiness. The fossils are preserved as mummified/compressed mericarps within 1.3‐million‐year‐old fluvio‐lacustrine sediments of the Funchal unit, Upper Volcanic complex, near Porto da Cruz. We assign them to the extant neoendemic species Melanoselinum (≡ Daucus) decipiens. The mericarp morphology shows remarkable stasis since the Calabrian stage of the Early Pleistocene. Our results demonstrate that in the Madeiran Daucinae clade, insular woodiness developed at least 1.3 million years ago, indicating a coeval or earlier immigration to Madeira Island of a Daucus sp. Our results reinforce the role of palaeobotanical research in oceanic islands, supported by stratigraphy and geochronology studies, as a key element for the understanding of plant palaeobiogeography, ecology and evolution worldwide. We expect this contribution to shed light on the evolutionary origins of carrots, and related plant groups, an important element of human food, and to better comprehend the evolution of plant insular woodiness.

A mantidfly in Cretaceous Spanish amber provides insights into the evolution of integumentary specialisations on the raptorial foreleg

Multiple predatory insect lineages have developed a raptorial lifestyle by which they strike and hold prey using modified forelegs armed with spine-like structures and other integumentary specialisations. However, how structures enabling the raptorial function evolved in insects remains largely hypothetical or inferred through phylogeny due to the rarity of meaningful fossils. This is particularly true for mantidflies (Neuroptera: Mantispidae), which have a scarce fossil record mostly based on rock compressions, namely isolated wings. Here, Aragomantispa lacerata gen. et sp. nov. is described from ca. 105-million-year-old San Just amber (Spain), representing the oldest and one of the few mantidflies hitherto described from amber. The fossil shows exquisitely preserved forefemoral spine-like structures composed of integumentary processes each bearing a modified seta, and prostrate setae on foretibiae and foretarsi. The fine morphology of these structures was unknown in fossil mantidflies. An assessment of integumentary specialisations from raptorial forelegs across mantispoid lacewings is provided. The present finding reveals how the specialised foreleg armature associated to the raptorial lifestyle in extant mantidflies was present yet not fully established by the Early Cretaceous, at least in some lineages, and provides palaeontological evidence supporting certain evolutionary patterns of acquisition of integumentary specialisations related to the raptorial function in the group.

A New Clevosaurid from the Triassic (Carnian) of Brazil and the Rise of Sphenodontians in Gondwana

The early evolution of lepidosaurs is marked by an extremely scarce fossil record during the Triassic. Importantly, most Triassic lepidosaur specimens are represented by disarticulated individuals from high energy accretion deposits in Laurasia, thus greatly hampering our understanding of the initial stages of lepidosaur evolution. Here, we describe the fragmentary remains of an associated skull and mandible of Clevosaurus hadroprodon sp. nov., a new taxon of sphenodontian lepidosaur from the Late Triassic (Carnian; 237–228 Mya) of Brazil. Referral to Sphenodontia is supported by the combined presence of a marginal dentition ankylosed to the apex of the dentary, maxilla, and premaxilla; the presence of ‘secondary bone’ at the bases of the marginal dentition; and a ventrally directed mental process at the symphysis of the dentary. Our phylogenetic analyses recover Clevosaurus hadroprodon as a clevosaurid, either in a polytomy with the Late Triassic to Early Jurassic Clevosaurus and Brachyrhinodon (under Bayesian inference), or nested among different species of Clevosaurus (under maximum parsimony). Clevosaurus hadroprodon represents the oldest known sphenodontian from Gondwana, and its clevosaurid relationships indicates that these sphenodontians achieved a widespread biogeographic distribution much earlier than previously thought.

A new desert-dwelling dinosaur (Theropoda, Noasaurinae) from the Cretaceous of south Brazil

Noasaurines form an enigmatic group of small-bodied predatory theropod dinosaurs known from the Late Cretaceous of Gondwana. They are relatively rare, with notable records in Argentina and Madagascar, and possible remains reported for Brazil, India, and continental Africa. In south-central Brazil, the deposits of the Bauru Basin have yielded a rich tetrapod fauna, which is concentrated in the Bauru Group. The mainly aeolian deposits of the Caiuá Group, on the contrary, bear a scarce fossil record composed only of lizards, turtles, and pterosaurs. Here, we describe the first dinosaur of the Caiuá Group, which also represents the best-preserved theropod of the entire Bauru Basin known to date. The recovered skeletal parts (vertebrae, girdles, limbs, and scarce cranial elements) show that the new taxon was just over 1 m long, with a unique anatomy among theropods. The shafts of its metatarsals II and IV are very lateromedially compressed, as are the blade-like ungual phalanges of the respective digits. This implies that the new taxon could have been functionally monodactyl, with a main central weight-bearing digit, flanked by neighbouring elements positioned very close to digit III or even held free of the ground. Such anatomical adaptation is formerly unrecorded among archosaurs, but has been previously inferred from footprints of the same stratigraphic unit that yielded the new dinosaur. A phylogenetic analysis nests the new taxon within the Noasaurinae clade, which is unresolved because of the multiple alternative positions that Noasaurus leali can acquire in the optimal trees. The exclusion of the latter form results in positioning the new dinosaur as the sister-taxon of the Argentinean Velocisaurus unicus.