Pleistocene mammals from Extinction Cave, Belize

A small mammalian fauna is recorded from Extinction Cave (also called Sibun Cave), east of Belmopan, on the Sibun River, Belize, Central America. The animals recognized are armadillo (†Dasypus bellus), American lion (†Panthera atrox), jaguar (Panthera onca), puma or mountain lion (Puma concolor), Florida spectacled bear (†Tremarctos floridanus), javelina or collared peccary (Pecari tajacu), llama (Camelidae indet., †?Palaeolama mirifica), red brocket deer (Mazama americana), bison (Bison sp.) and Mexican half-ass (†Equus conversidens); sabre-toothed cat (†Smilodon fatalis) may also be represented. “†” indicates an extinct taxon. Bear and bison are absent from the region today. The bison record is one of the more southerly known. The bear record is almost the most westerly known and a first for Central America.

Were the synapsids primitively endotherms? A palaeohistological approach using phylogenetic eigenvector maps

The acquisition of mammalian endothermy is poorly constrained both phylogenetically and temporally. Here, we inferred the resting metabolic rates (RMRs) and the thermometabolic regimes (endothermy or ectothermy) of a sample of eight extinct synapsids using palaeohistology, phylogenetic eigenvector maps (PEMs), and a sample of 17 extant tetrapods of known RMR (quantified using respirometry). We inferred high RMR values and an endothermic metabolism for the anomodonts ( Lystrosaurus sp., Oudenodon bainii ) and low RMR values and an ectothermic metabolism for Clepsydrops collettii, Dimetrodon sp., Edaphosaurus boanerges, Mycterosaurus sp., Ophiacodon uniformis and Sphenacodon sp. A maximum-likelihood ancestral states reconstruction of RMRs performed using the values inferred for extinct synapsids, and the values measured using respirometry in extant tetrapods, shows that the nodes Anomodontia and Mammalia were primitively endotherms. Finally, we performed a parsimony optimization of the presence of endothermy using the results obtained in the present study and those obtained in previous studies that used PEMs. For this, we assigned to each extinct taxon a thermometabolic regime (ectothermy or endothermy) depending on whether the inferred values were significantly higher, lower or not significantly different from the RMR value separating ectotherms from endotherms (1.5 ml O 2 h −1 g −0.67 ). According to this optimization, endothermy arose independently in Archosauromorpha, Sauropterygia and Therapsida. This article is part of the theme issue ‘Vertebrate palaeophysiology’.

Stretched, mangled, and torn: Responses of the Ediacaran fossil Dickinsonia to variable forces

Dickinsonia is one of the oldest macroscopic metazoans in the fossil record. Determining the biological characters of this extinct taxon is critical to our understanding of the early evolution of life. Preservation of abundant specimens from the Ediacara Member (Rawnsley Quartzite), South Australia, in a variety of taphonomic states allows the unparalleled opportunity to compare the biomechanical responses of Dickinsonia tissue to various forces with those typical of modern organisms. Dickinsonia are found as lifted, transported, folded, rolled, ripped, and expanded or contracted individuals, while maintaining diagnostic morphology. This suite of characters indicates that Dickinsonia was composed of material that was flexible, difficult to rip, and capable of elastic and plastic deformation. While none of these traits are diagnostic of a single biomaterial component, we find many similarities with modern biopolymers, particularly collagen, keratin, and elastin. Maintenance of significant relief following complete tearing suggests that Dickinsonia was composed of relatively thick tissues, signifying higher oxygen requirements than previously hypothesized. The ability to be transported and still be preserved as recognizable fossils is unique amongst the Ediacara Biota and demonstrates that Dickinsonia was a taphonomic elite. Combined with discovery in multiple environmental settings, this indicates that the absence of Dickinsonia represents the likely extinction of this organism prior to the Nama assemblage, possibly due to a decrease in the global availability of oxygen in the latest Ediacaran.

Resurrection of a regionally extinct taxon in Croatia – the case of Ammophila arenaria (L.) Link (Poaceae)

A regionally extinct taxon, Ammophila arenaria (L.) Link subsp. arundinacea H. Lindb., has been rediscovered in the Croatian flora after 78 years. Previously it was known only from two coastal sand dune sites in Northern Dalmatia. The habitat at the locality of Crnika near Lopar on the northern Adriatic island of Rab is destroyed and A. arenaria subsp. arundinacea does not grow there anymore. At the second locality, on the sand dunes of Kraljičina plaža in the vicinity of the town of Nin, A. arenaria subsp. arundinacea was rediscovered and confirmed after 174 years. This is the only population of this taxon in Croatia, counting 48 mature individuals where the psammophylous habitat of Kraljičina plaža is under strong anthropogenic influence. This taxon is now classified as critically endangered (CR) and merits adequate active protection and conservation of its psammophylous habitat.

Resolving the phylogenetic position of Darwin's extinct ground sloth ( Mylodon darwinii ) using mitogenomic and nuclear exon data

Mylodon darwinii is the extinct giant ground sloth named after Charles Darwin, who first collected its remains in South America. We have successfully obtained a high-quality mitochondrial genome at 99-fold coverage using an Illumina shotgun sequencing of a 12 880-year-old bone fragment from Mylodon Cave in Chile. Low level of DNA damage showed that this sample was exceptionally well preserved for an ancient subfossil, probably the result of the dry and cold conditions prevailing within the cave. Accordingly, taxonomic assessment of our shotgun metagenomic data showed a very high percentage of endogenous DNA with 22% of the assembled metagenomic contigs assigned to Xenarthra. Additionally, we enriched over 15 kb of sequence data from seven nuclear exons, using target sequence capture designed against a wide xenarthran dataset. Phylogenetic and dating analyses of the mitogenomic dataset including all extant species of xenarthrans and the assembled nuclear supermatrix unambiguously place Mylodon darwinii as the sister-group of modern two-fingered sloths, from which it diverged around 22 million years ago. These congruent results from both the mitochondrial and nuclear data support the diphyly of the two modern sloth lineages, implying the convergent evolution of their unique suspensory behaviour as an adaption to arboreality. Our results offer promising perspectives for whole-genome sequencing of this emblematic extinct taxon.

Walk before you jump: new insights on early frog locomotion from the oldest known salientian

Understanding the evolution of a Bauplan starts with discriminating phylogenetic signal from adaptation and the latter from exaptation in the observed biodiversity. Whether traits have predated, accompanied, or followed evolution of particular functions is the basic inference to establish the type of explanations required to determine morphological evolution. To accomplish this, we focus in a particular group of vertebrates, the anurans. Frogs and toads have a unique Bauplan among vertebrates, with a set of postcranial features that have been considered adaptations to jumping locomotion since their evolutionary origin. This interpretation is frequently stated but rarely tested in scientific literature. We test this assumption reconstructing the locomotor capabilities of the earliest known salientian, Triadobatrachus massinoti. This extinct taxon exhibits a mosaic of features that have traditionally been considered as representing an intermediate stage in the evolution of the anuran Bauplan, some of which were also linked to jumping skills. We considered T. massinoti in an explicit evolutionary framework by means of multivariate analyses and comparative phylogenetic methods. We used length measurements of major limb bones of 188 extant limbed amphibians (frogs and salamanders) and lizards as a morphological proxy of observed locomotor behavior. Our findings show that limb data correlate with locomotion, regardless of phylogenetic relatedness, and indicate that salamander-like lateral undulatory movements were the main mode of locomotion of T. massinoti. These results contrast with recent hypotheses and indicate that derived postcranial features that T. massinoti shared with anurans might have been later co-opted as exaptations in jumping frogs.

The role of rock mining for maintaining Dauco carotae-Crepidetum rhoeadifoliae Hejný et Grüll in Hejný et al. 1979 — a new to Poland plant association

This work presents the Dauco carotae-Crepidetum rhoeadifoliae plant association, which is new to Poland. The association has been observed in industrial reclamation areas in the vicinity of carbonate mineral excavation sites in the central part of the Opole region. In the vast majority of cases, plots of this association developed in reclaimed areas. The majority of diagnostic species for the association was found within surveyed plots, including Verbascum thapsus, V. densiflorum and Bryum argenteum. Taxa characteristic of the alliance were also constantly present, i.e. Daucus carota, Melilotus alba, M. officinalis, Echium vulgare and Erysimum hieracifolium. This association belongs to the rarest syntaxa in Poland included in the Dauco-Melilotion alliance of ruderal communities with a predominance of hemicryptophytes, therophytes and perennials. The main diagnostic species — Crepis rhoeadifolia, belongs to very rare elements of Polish flora. It has been observed only in the southern part of the country in approx. 20 sites. Crepis rhoeadifolia had not been observed in Silesia for approx. 40 years, which is why it was considered to be an extinct taxon in this region. Rediscovering of the species allowed for diagnosing the Dauco-Crepidetum rhoeadifoliae association. This association is an example of a pioneer phytocenosis of, most likely, anthropogenic origin in Silesia.

On the identity of Monsieur Dussumier’s Dutch tortoise and the lectotype of Testudo dussumieri Gray, 1831

Although it was forgotten for over a century, the binomen Testudo dussumieri Gray, 1831, is an available name, and the specimen RMNH 3231 deposited in the natural history museum of Leiden – evidently one of the two original syntypes of T. dussumieri – has been designated as the lectotype of this taxon. Recently several authors have actively promoted this as the name-bearing type for the Aldabra tortoise, escalating debates in which this chelonian has been immersed for nearly two decades. This lectotype designation is highly significant to nomenclatural and taxonomic disputes regarding tortoises (Testudinidae), living and extinct, from the western Indian Ocean; and an attempt has been made in this paper to compile all information relevant to the lectotype as well as to better understand the history of the binomen applied to it. Several critical aspects of the history are uncertain and open to speculation. The provenance of RMNH 3231 is unknown and unlikely to be Aldabra Atoll; the specimen was most likely collected in the granitic Seychelles, between 1823 and 1829. The combination of estimated date and locality of collection raises the possibility that the lectotype is not an Aldabra tortoise, but rather an extinct taxon from the granitic Seychelles. It is concluded that RMNH 3231 is not a suitable name-bearing type for the Aldabra tortoise, and the continued use of the name T. dussumieri will cause persistent nomenclatural and taxonomic confusion and unending debate.