Synopsis Recently-developed, molecularly-based phylogenies of geckos have provided the basis for reassessing the number of times adhesive toe-pads have arisen within the Gekkota. At present both a single origin and multiple origin hypotheses prevail, each of which has consequences that relate to explanations about digit form and evolutionary transitions underlying the enormous variation in adhesive toe pad structure among extant, limbed geckos (pygopods lack pertinent features). These competing hypotheses result from mapping the distribution of toe pads onto a phylo- genetic framework employing the simple binary expedient of whether such toe pads are present or absent. It is evident, however, that adhesive toe pads are functional complexes that consist of a suite of integrated structural components that interact to bring about adhesive contact with the substratum and release from it. We evaluated the competing hypotheses about toe pad origins using 34 features associated with digit structure (drawn from the overall form of the digits; the presence and form of adhesive scansors; the proportions and structure of the phalanges; aspects of digital muscular and tendon morphology; presence and form of paraphalangeal elements; and the presence and form of substrate compliance-enhancing structures). We mapped these onto a well-supported phylogeny to reconstruct their evolution. Nineteen of these characters proved to be informative for all extant, limbed geckos, allowing us to assess which of them exhibit co- occurrence and/or clade-specificity. We found the absence of adhesive toe pads to be the ancestral state for the extant Gekkota as a whole, and our data to be consistent with independent origins of adhesive toe pads in the Diplodactylidae, Sphaerodactylidae, Phyllodactylidae, and Gekkonidae, with a strong likelihood of multiple origins in the latter three families. These findings are consistent with recently-published evidence of the presence of adhesively-competent digits in geckos generally regarded as lacking toe pads. Based upon morphology we identify other taxa at various locations within the gekkotan tree that are promising candidates for the expression of the early phases of adhesively-assisted locomotion. Investigation of functionally transitional forms will be valuable for enhancing our understanding of what is necessary and sufficient for the transition to adhesively-assisted locomotion, and for those whose objectives are to develop simulacra of the gekkotan adhesive system for biotechnological applications.
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Cretaceous fossil gecko hand reveals a strikingly modern scansorial morphology: Qualitative and biometric analysis of an amber-preserved lizard hand
Gekkota (geckos and pygopodids) is a clade thought to have originated in the Early Cretaceous and that today exhibits one of the most remarkable scansorial capabilities among lizards. Little information is available regarding the origin of scansoriality, which subsequently became widespread and diverse in terms of ecomorphology in this clade. An undescribed amber fossil (MCZ R–190835) from mid-Cretaceous outcrops of the north of Myanmar dated at 99 Ma, previously assigned to stem Gekkota, preserves carpal, metacarpal and phalangeal bones, as well as supplementary climbing structures, such as adhesive pads and paraphalangeal elements. This fossil documents the presence of highly specialized adaptive structures. Here, we analyze in detail the manus of the putative stem Gekkota. We use morphological comparisons in the context of extant squamates, to produce a detailed descriptive analysis and a linear discriminant analysis (LDA) based on 32 skeletal variables of the manus. The comparative sample includes members of 15 extant squamate families (Agamidae, Dactyloidae, Iguanidae, Leiosauridae, Liolaemidae, Polychrotidae, Tropiduridae, Diplodactylidae, Eublepharidae, Gekkonidae, Phyllodactylidae, Sphaerodactylidae, Gymnophthalmidae, Teiidae, and Scincidae). Although the fossil manus is qualitatively more similar to that of members of Gekkota, the LDA analysis places it in a morphozone shared by Gekkota and Scincomorpha. This result is particularly interesting, given that despite the presence of paraphalangeal structures had only been reported in extant geckos of the families Gekkonidae and Phyllodactylidae, the usage of an adhesive subdigital system to climb originated independently in Gekkota, Scincidae, and Dactyloidae.
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- Award ID(s):
- 1657656
- NSF-PAR ID:
- 10092690
- Date Published:
- Journal Name:
- Cretaceous research
- Volume:
- 84
- ISSN:
- 1095-998X
- Page Range / eLocation ID:
- 120-133
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Genomic resources across squamate reptiles (lizards and snakes) have lagged behind other vertebrate systems and high-quality reference genomes remain scarce. Of the 23 chromosome-scale reference genomes across the order, only 12 of the ~60 squamate families are represented. Within geckos (infraorder Gekkota), a species-rich clade of lizards, chromosome-level genomes are exceptionally sparse representing only two of the seven extant families. Using the latest advances in genome sequencing and assembly methods, we generated one of the highest-quality squamate genomes to date for the leopard gecko, Eublepharis macularius (Eublepharidae). We compared this assembly to the previous, short-read only, E. macularius reference genome published in 2016 and examined potential factors within the assembly influencing contiguity of genome assemblies using PacBio HiFi data. Briefly, the read N50 of the PacBio HiFi reads generated for this study was equal to the contig N50 of the previous E. macularius reference genome at 20.4 kilobases. The HiFi reads were assembled into a total of 132 contigs, which was further scaffolded using HiC data into 75 total sequences representing all 19 chromosomes. We identified 9 of the 19 chromosomal scaffolds were assembled as a near-single contig, whereas the other 10 chromosomes were each scaffolded together from multiple contigs. We qualitatively identified that the percent repeat content within a chromosome broadly affects its assembly contiguity prior to scaffolding. This genome assembly signifies a new age for squamate genomics where high-quality reference genomes rivaling some of the best vertebrate genome assemblies can be generated for a fraction of previous cost estimates. This new E. macularius reference assembly is available on NCBI at JAOPLA010000000.
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The neogastropod clade Conoidea includes the familiar cone snails (Conidae) and 17 additional families, all but one of which (Cryptoconidae) are extant. There are over 5,000 extant species and 380 genera of Conoidea, all of which are venomous predators. Many conoideans other than Conidae and Terebridae (auger snails) are often called “turrids” and are often characterized by the presence of an indented “turrid notch” at the terminal edge of the shell's sutural ramp. Conoideans have a rich fossil record that extends to the Cretaceous, but a combination of hyperdiversity, subtle differences between species, often small shell size, and taxonomic complexity has resulted in them being little studied, despite their evolutionary success. We have begun to explore the fossil record of conoideans from the Plio-Pleistocene of the southeastern United States as part of a broader project to catalog and document the fossil records of all gastropod and bivalve species from this system. A newly developed database derived from literature and museum collections shows that nearly 200 species-group names have been applied to conoideans (excluding Conidae) from this system, fewer than 10 of which were described in the past 50 years. We present preliminary assessments of the Pliocene to Recent diversity patterns of individual subclades from the Southeast. Preliminary data from the Paleobiology Database demonstrate that occurrences assigned to the conoidean family Turridae from this study region are much less likely to be assigned to species than most other co-occurring mollusk families, with about 56% of occurrences assigned to a species. Online specimen data derived from the Florida Museum of Natural History similarly show that just under 50% of records from this system assigned to Turridae are also assigned to species. Because records unidentified to species are unevenly distributed among molluscan families, attempts to restrict analyses to only records which are well-resolved taxonomically may impact our overall understanding of biodiversity and ecology, especially when they result in the exclusion of species-rich clades. Our results highlight the importance of primary systematic research and museum collections for assessing important but understudied components of the biodiversity of fossil molluscan faunas.more » « less
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Abstract Chalcidoidea are mostly parasitoid wasps that include as many as 500 000 estimated species. Capturing phylogenetic signal from such a massive radiation can be daunting. Chalcidoidea is an excellent example of a hyperdiverse group that has remained recalcitrant to phylogenetic resolution. We combined 1007 exons obtained with Anchored Hybrid Enrichment with 1048 ultra‐conserved elements (UCEs) for 433 taxa including all extant families, >95% of all subfamilies, and 356 genera chosen to represent the vast diversity of the superfamily. Going back and forth between the molecular results and our collective knowledge of morphology and biology, we detected bias in the analyses that was driven by the saturation of nucleotide data. Our final results are based on a concatenated analysis of the least saturated exons and UCE datasets (2054 loci, 284 106 sites). Our analyses support an expected sister relationship with Mymarommatoidea. Seven previously recognized families were not monophyletic, so support for a new classification is discussed. Natural history in some cases would appear to be more informative than morphology, as illustrated by the elucidation of a clade of plant gall associates and a clade of taxa with planidial first‐instar larvae. The phylogeny suggests a transition from smaller soft‐bodied wasps to larger and more heavily sclerotized wasps, with egg parasitism as potentially ancestral for the entire superfamily. Deep divergences in Chalcidoidea coincide with an increase in insect families in the fossil record, and an early shift to phytophagy corresponds with the beginning of the “Angiosperm Terrestrial Revolution”. Our dating analyses suggest a middle Jurassic origin of 174 Ma (167.3–180.5 Ma) and a crown age of 162.2 Ma (153.9–169.8 Ma) for Chalcidoidea. During the Cretaceous, Chalcidoidea may have undergone a rapid radiation in southern Gondwana with subsequent dispersals to the Northern Hemisphere. This scenario is discussed with regard to knowledge about the host taxa of chalcid wasps, their fossil record and Earth's palaeogeographic history.
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Summary Lycopodiaceae are one of three surviving families of lycopsids, a lineage of vascular plants with a fossil history dating to at least the Early Devonian or perhaps the Late Silurian (
c . 415 Ma). Many fossils have been linked to crown Lycopodiaceae, but the lack of well‐preserved material has hindered definitive recognition of this group in the paleobotanical record.New, exceptionally well‐preserved permineralized lycopsid fossils from the Early Cretaceous (125.6 ± 1.0 Ma) of Inner Mongolia, China, were examined in detail using acetate peel and micro‐computed tomography techniques. The anatomy of extant Lycopodiaceae was analyzed for comparison using fluorescence microscopy. Phylogenetic relationships of the new fossil to extant Lycopodiaceae were evaluated using parsimony and maximum likelihood analyses.
Lycopodicaulis oellgaardii gen. et sp. nov. provides the earliest unequivocal and best‐documented evidence of crown Lycopodiaceae and Lycopodioideae, based on anatomically‐preserved fossil material.Recognition of
Lycopodicaulis in Asia during the Early Cretaceous indicates the presence of crown Lycopodiaceae at this time, and striking similarities of stem anatomy with extant species provide a framework for the understanding of the interaction of branching and vascular anatomy in crown‐group lycopsids.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/doi.org/10.1016/j.cretres.2017.11.003
