The extinct neoteleost family Dercetidae includes elongate, long-jawed marine fishes that are known from the Late Cretaceous to Paleocene in deposits from the Levant, Europe, North Africa, England, Mexico and Brazil. The fossil record of...
moreThe extinct neoteleost family Dercetidae includes elongate, long-jawed marine fishes that are known from the Late Cretaceous to Paleocene in deposits from the Levant, Europe, North Africa, England, Mexico and Brazil. The fossil record of the family in South America is very sparse and previously was restricted to outcrops in Brazil. Herein we describe a new dercetid fish from the Turonian of Colombia, †Candelarhynchus padillai gen. et sp. nov. A single articulated specimen is preserved in part and counterpart; the posterior part of the fish is missing. The specimen differs from other dercetid species by the following unique combination of morphological features: lack of scutes on the flanks of the body, presence of a single pair of transverse processes associated with the abdominal vertebrae, roofed posttemporal fossa, single row of small conical teeth on the dentary and maxilla, toothless premaxilla ornamented with pronounced longitudinal striations and protruding forward far beyond the anterior end of the dentary, and relatively large pectoral fins positioned high on the body. When included in a phylogenetic analysis of †Enchodontoidei, †C. padillai gen. et sp. nov. falls within a monophyletic family Dercetidae and is placed as sister taxon to the Late Cretaceous dercetid †Hastichthys from Israel, indicating faunal connections between the Eastern and Western Tethys. The new taxon provides novel insights into the distribution of dercetid fishes in the Western Tethys region during the early Late Cretaceous.
http://zoobank.org/urn:lsid:zoobank.org:pub:29F97139-98BD-48E5-AAC0-091980F866E2Summary True crabs (Brachyura) are one of the few groups of arthropods to evolve several types of compound eye, the origins and early evolution of which are obscure. Here, we describe details of the eyes of the Cretaceous brachyuran...
moreSummary True crabs (Brachyura) are one of the few groups of arthropods to evolve several types of compound eye, the origins and early evolution of which are obscure. Here, we describe details of the eyes of the Cretaceous brachyuran Callichimaera perplexa, which possessed remarkably large eyes and a highly disparate body form among brachyurans. The eyes of C. perplexa preserve internal optic neuropils and external corneal elements, and it is the first known post-Paleozoic arthropod to preserve both. Additionally, a series of specimens of C. perplexa preserve both the eyes and carapace, allowing for the calculation of the optical growth rate. C. perplexa shows the fastest optical growth rate compared with a sample of 14 species of extant brachyurans. The growth series of C. perplexa, in combination with the calculation of the interommatidial angle and eye parameter, demonstrates that it was a highly visual predator that inhabited well-lit environments.
Eubrachyurans, or ‘higher’ true crabs, are the most speciose group of decapod crustaceans and have a rich fossil record extending into the Early Cretaceous. However, most extant families are first found in the fossil record in the...
moreEubrachyurans, or ‘higher’ true crabs, are the most speciose group of decapod crustaceans and have a rich fossil record extending into the Early Cretaceous. However, most extant families are first found in the fossil record in the Palaeogene, and particularly in the Eocene. Unfortunately, fossils of many early eubrachyuran groups are often fragmentary, and only a few studies have combined extinct and extant taxa in a phylogenetic context using different optimality criteria. Here, we report the dairoidid crab Phrynolambrus sagittalis sp. nov., an enigmatic eubrachyuran from the upper Eocene of Huesca (northern Spain), whose completeness and exquisite preservation permit examination of its anatomy in a phylogenetic context. Dairoidids have previously been considered among the oldest stone crabs (Eriphioidea) or elbow crabs (Parthenopoidea), two disparate and distantly related groups of true crabs living today. Mechanical preparation and computed tomography of the fossil material revea...
ABSTRACTDespite the rich paleontological heritage of Colombia, in the equatorial Neotropics, one of the least explored regions in terms of its fossil record is the Putumayo region near Ecuador, largely due to its considerable ground...
moreABSTRACTDespite the rich paleontological heritage of Colombia, in the equatorial Neotropics, one of the least explored regions in terms of its fossil record is the Putumayo region near Ecuador, largely due to its considerable ground cover, thick vegetation, rock weathering, geographic remoteness, and overall inaccessibility to well-exposed outcrops. This precludes detailed comparisons with neighboring basins, and thus the generation of more comprehensive biostratigraphic correlations for western northern South America and other paleobiogeographic regions, e.g., Mediterranean Tethys, northern Africa, Western Interior Basin. Here, we report 67 occurrences of mid- Cretaceous ammonoids and other macrofossils (e.g., bivalves, decapod crustaceans, fish remains, plant remains), from the middle Albian of the uppermost Caballos Formation and the upper Albian–lower Cenomanian of the lower Villeta Formation, collected in-situ from a stratigraphic section cropping out on the Mocoa–San Francisco...
For much of terrestrial biodiversity, the evolutionary pathways of adaptation from marine ancestors are poorly understood, and have usually been viewed as a binary trait. True crabs, the decapod crustacean infraorder Brachyura, comprise...
moreFor much of terrestrial biodiversity, the evolutionary pathways of adaptation from marine ancestors are poorly understood, and have usually been viewed as a binary trait. True crabs, the decapod crustacean infraorder Brachyura, comprise over 7,600 species representing a striking diversity of morphology and ecology, including repeated adaptation to non-marine habitats. Here, we reconstruct the evolutionary history of Brachyura using new and published sequences of 10 genes for 344 tips spanning 88 of 109 brachyuran families. Using 36 newly vetted fossil calibrations, we infer that brachyurans most likely diverged in the Triassic, with family-level splits in the late Cretaceous and early Paleogene. By contrast, the root age is underestimated with automated sampling of 328 fossil occurrences explicitly incorporated into the tree prior, suggesting such models are a poor fit under heterogeneous fossil preservation. We apply recently defined trait-by-environment associations to classify a ...
Fossils are critically important for evolutionary studies as they provide the link between geological ages and the phylogeny of life. The Pancrustacea are an incredibly diverse clade, representing over 800,000 described extant species,...
moreFossils are critically important for evolutionary studies as they provide the link between geological ages and the phylogeny of life. The Pancrustacea are an incredibly diverse clade, representing over 800,000 described extant species, encompassing a variety of familiar and unfamiliar forms, such as ostracods, tongue worms, crabs, lobsters, shrimps, copepods, barnacles, branchiopods, remipedes, and insects. Having colonized nearly every environment on Earth, from hydrothermal vents to terrestrial habitats, they have a diverse fossil record dating back to the Cambrian (540–485 Ma). The quality of the fossil record of each clade is variable and related to their lifestyle (e.g., free-living versus parasitic, benthic versus pelagic) and the degree of mineralization of their cuticle. We review the systematics, morphology, preservation, and paleoecology of pancrustacean fossils; each major clade is discussed in turn, and, where possible, fossil systematics are compared with more recent da...
A new genus and species of eubrachyuran crab, Ancipitecancer collinsi, are recorded from lower Pleistocene strata exposed in the Poggi Gialli quarry (Sinalunga, Tuscany, central Italy). This new form is unlike any fossil or extant crab...
moreA new genus and species of eubrachyuran crab, Ancipitecancer collinsi, are recorded from lower Pleistocene strata exposed in the Poggi Gialli quarry (Sinalunga, Tuscany, central Italy). This new form is unlike any fossil or extant crab species known to us. The overall carapace shape and dorsal configuration of Ancipitecancer nov. gen. fit the Eubrachyura well, and among eubrachyurans we assign it tentatively to the Xanthoidea sensu lato. Although xanthoid-like crabs are amongst the most anatomically diverse groups of true crabs, the unusual body of Ancipitecancer nov. gen. cannot be accommodated within any brachyuran family currently recognised.
Despite the extensive fossil record of higher crabs (Eubrachyura) from Late Cretaceous and Cenozoic rocks worldwide, their Early Cretaceous occurrences are scarce and fragmentary, obscuring our understanding of their early evolution....
moreDespite the extensive fossil record of higher crabs (Eubrachyura) from Late Cretaceous and Cenozoic rocks worldwide, their Early Cretaceous occurrences are scarce and fragmentary, obscuring our understanding of their early evolution. Until now, representatives of only two families of eubrachyuran‐like crabs were known from the Early Cretaceous: Componocancridae and Tepexicarcinidae fam. nov., both monospecific lineages from the Albian (~110–100 Ma) of North and Central America, respectively. The discovery of Telamonocarcinus antiquus sp. nov. (Telamonocarcinidae) from the early Albian of Colombia, South America (~110 Ma), increases to three the number of known Early Cretaceous eubrachyuran‐like families. The ages and geographical distributions of the oldest eubrachyuran‐like taxa (i.e. Componocancridae, Telamonocarcinidae and Tepexicarcinidae fam. nov.) suggest that the oldest higher true crabs might have originated in the Americas; that they were already morphologically diverse by ...
With over 15,000 extant species, Decapoda—or ten-legged crustaceans such as crabs, shrimp, lobsters, and relatives— are among the most speciose and economically important group of crustaceans. Despite of their diversity, anatomical...
moreWith over 15,000 extant species, Decapoda—or ten-legged crustaceans such as crabs, shrimp, lobsters, and relatives— are among the most speciose and economically important group of crustaceans. Despite of their diversity, anatomical disparity, and remarkable fossil record extending back to the Late Paleozoic, the origins of Decapoda and their phylogenetic relationships with eumalacostracans remains elusive and inconclusive. Molecular dating suggests that decapods originated in the Late Ordovician (~450 Mya), but no reliable fossil crown groups are found until the Late Devonian. Moreover, there is no consensus on which lineages belong to stem groups, obscuring our understanding of the roots of the ten-legged decapod body plans as a whole, and how they relate to other non-decapod crustaceans. We present new, exceptional fossils from the Late Devonian of Czech Republic and Poland that belong to †Angustidontida, an odd shrimp-looking crustacean with a combination of anatomical features u...
Recognition of remains of sterna, pleons, and pereiopods of Aulavescus paintenensis n. sp. (Munidopsidae) and Goniodromites serratus Beurlen, 1929, from the Late Jurassic Solnhofentype lagerstätten in Bavaria, Germany, provides the first...
moreRecognition of remains of sterna, pleons, and pereiopods of Aulavescus paintenensis n. sp. (Munidopsidae) and Goniodromites serratus Beurlen, 1929, from the Late Jurassic Solnhofentype lagerstätten in Bavaria, Germany, provides the first description of these structures in Jurassic Munidopsidae and Goniodromitidae. Addition of these morphological characters to Goniodromitidae and cladistic analysis secured the position of the family within Homolodromioidea and Dromiacea.
The Brachyura, or ‘true’ crabs, are the most derived and diverse group of crustaceans. They are first known from the Mid–Jurassic (~160 Ma.) and rapidly diversified worldwide during the Cretaceous (~146 to 66 Ma.). Since then, crabs have...
moreThe Brachyura, or ‘true’ crabs, are the most derived and diverse group of crustaceans. They are first known from the Mid–Jurassic (~160 Ma.) and rapidly diversified worldwide during the Cretaceous (~146 to 66 Ma.). Since then, crabs have exploded in form and function, resulting in the incredible morphological diversity seen among the more than ~9,000 fossil and extant species. Despite the large disparity of their body plans, various molecular, morphological and spermatological studies have shown that Brachyura is a monophyletic group, sister to Anomura (i.e hermit crabs and allies). Nevertheless, the oldest brachyurans are anatomically very different from the rest of higher crab clades, obscuring their phylogenetic relationships. Previous and recent field works in Early Cretaceous rocks of Santander, Colombia (Zapatoca, from 1983 to 2012; San Vicente de Chucurí, 2013) have yielded more than 400 specimens of a dozen ancient brachyuran crab species (Luque et al., in progress). Based o...
Peracarida (e.g. woodlice and side-swimmers) are, together with their sister-group Eucarida (e.g. krill and decapods), the most speciose group of modern crustaceans, suggested to have appeared as early as the Ordovician. While...
morePeracarida (e.g. woodlice and side-swimmers) are, together with their sister-group Eucarida (e.g. krill and decapods), the most speciose group of modern crustaceans, suggested to have appeared as early as the Ordovician. While eucarids' incursion onto land consists of mainly freshwater and littoral grounds, some peracarids have evolved fully terrestrial ground-crawling ecologies, inhabiting even our gardens in temperate regions (e.g. pillbugs and sowbugs). Their fossil record extends back to the Carboniferous and consists mainly of marine occurrences. Here, we provide a complete re-analysis of a fossil arthropod— Oxyuropoda— reported in 1908 from the Late Devonian floodplains of Ireland, and left with unresolved systematic affinities despite a century of attempts at identification. Known from a single specimen preserved in two dimensions, we analysed its anatomy using digital microscopy and multispectral macroimaging to enhance the contrast of morphological structures. The new a...
A fundamental question in biology is whether phenotypes can be predicted by ecological or genomic rules. At least five cases of convergent evolution of the crab‐like body plan (with a wide and flattened shape, and a bent abdomen) are...
moreA fundamental question in biology is whether phenotypes can be predicted by ecological or genomic rules. At least five cases of convergent evolution of the crab‐like body plan (with a wide and flattened shape, and a bent abdomen) are known in decapod crustaceans, and have, for over 140 years, been known as “carcinization.” The repeated loss of this body plan has been identified as “decarcinization.” In reviewing the field, we offer phylogenetic strategies to include poorly known groups, and direct evidence from fossils, that will resolve the history of crab evolution and the degree of phenotypic variation within crabs. Proposed ecological advantages of the crab body are summarized into a hypothesis of phenotypic integration suggesting correlated evolution of the carapace shape and abdomen. Our premise provides fertile ground for future studies of the genomic and developmental basis, and the predictability, of the crab‐like body form.
ABSTRACTImage-forming compound eyes are such a valuable adaptation that similar visual systems have evolved independently across crustaceans. But if different compound eye types have evolved independently multiple times, how useful are...
moreABSTRACTImage-forming compound eyes are such a valuable adaptation that similar visual systems have evolved independently across crustaceans. But if different compound eye types have evolved independently multiple times, how useful are eye structures and ommatidia morphology for resolving phylogenetic relationships? Crabs are ideal study organisms to explore these questions because they have a good fossil record extending back into the Jurassic, they possess a great variety of optical designs, and details of eye form can be compared between extant and fossil groups. True crabs, or Brachyura, have been traditionally divided into two groups based on the position of the sexual openings in males and females: the so-called ‘Podotremata’ (females bearing their sexual openings on the legs), and the Eubrachyura, or ‘higher’ true crabs (females bearing their sexual openings on the thorax). Although Eubrachyura appears to be monophyletic, the monophyly of podotreme crabs remains controversial...
Evolutionary origins of novel forms are often obscure because early and transitional fossils tend to be rare, poorly preserved, or lack proper phylogenetic contexts. We describe a new, exceptionally preserved enigmatic crab from the...
moreEvolutionary origins of novel forms are often obscure because early and transitional fossils tend to be rare, poorly preserved, or lack proper phylogenetic contexts. We describe a new, exceptionally preserved enigmatic crab from the mid-Cretaceous of Colombia and the United States, whose completeness illuminates the early disparity of the group and the origins of novel forms. Its large and unprotected compound eyes, small fusiform body, and leg-like mouthparts suggest larval trait retention into adulthood via heterochronic development (pedomorphosis), while its large oar-like legs represent the earliest known adaptations in crabs for active swimming. Our phylogenetic analyses, including representatives of all major lineages of fossil and extant crabs, challenge conventional views of their evolution by revealing multiple convergent losses of a typical “crab-like” body plan since the Early Cretaceous. These parallel morphological transformations may be associated with repeated invasio...