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1,301 results for “Early Cretaceous”
Data from: Quantifying the gastral mass in Early Cretaceous ornithuromorphs (Aves: Ornithothoraces) from the Jehol avifauna
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Data from: A new ophthalmosaurid ichthyosaur from the early Cretaceous of Colombia
Cretaceous ichthyosaurs were relatively diverse in temperate latitudes, but few species have been described from the palaeotropics. Here, we describe a new ophthalmosaurid ichthyosaur, Muiscasaurus catheti gen. et sp. nov., from the Barremian–Aptian aged Paja Formation of Colombia. This species is known only from a partial skull and differs from all other ichthyosaurs in the unusual configuration of the external narial opening, slender rostrum, narrow postorbital region, and gracile dentition. It is the second ichthyosaur described from the Paja Formation, suggesting moderate taxonomic and ecological ichthyosaur diversity in the region during the Early Cretaceous.
Data from: Highly resolved early Eocene food webs show development of modern trophic structure after the end-Cretaceous extinction
Generalities of food web structure have been identified for extant ecosystems. However, the trophic organization of ancient ecosystems is unresolved, as prior studies of fossil webs have been limited by low-resolution, high-uncertainty data. We compiled highly resolved, well-documented feeding interaction data for 700 taxa from the 48 million-year-old latest early Eocene Messel Shale, which contains a species assemblage that developed after an interval of protracted environmental and biotal change during and following the end-Cretaceous extinction. We compared the network structure of Messel lake and forest food webs to extant webs using analyses that account for scale dependence of structure with diversity and complexity. The Messel lake web, with 94 taxa, displays unambiguous similarities in structure to extant webs. While the Messel forest web, with 630 taxa, displays differences compared to extant webs, they appear to result from high diversity and resolution of insect–plant interactions, rather than substantive differences in structure. The evidence presented here suggests that modern trophic organization developed along with the modern Messel biota during an 18 Myr interval of dramatic post-extinction change. Our study also has methodological implications, as the Messel forest web analysis highlights limitations of current food web data and models.
Data from: Ecological stasis in Spinicaudata (Crustacea, Branchiopoda)? Early Cretaceous clam shrimp of the Yixian Formation of north‐east China occupied a broader realized ecological niche than extant members of the group
The palaeoecology of Spinicaudata, the dominant group of benthic invertebrates in many pre-Cenozoic freshwater environments, remains poorly understood. In analogy with extant taxa, it has been oversimplified and often reduced to shallow, temporary environments characterised by few trophic levels, implying ecological stasis from the Devonian to the Recent. We excavated 43 horizons of the Lower Cretaceous Yixian Formation (Anjiagou and Hengdaozi beds) to evaluate whether spinicaudatan ecology can be simplified to such an extent. Sedimentological evidence suggests general perennial conditions during the excavated lake interval. Based on 33,226 specimen counts, we identified three arthropod-dominated macrobenthic associations and two assemblages. Response curves indicate that the spinicaudatan Eosestheria middendorfii was exceptionally tolerant to environmental gradients, followed, in decreasing order, by mayfly larvae, water boatmen and oligochaetes. Also, many spinicaudatan-yielding layers represent death after reproductive senescence rather than mass-mortality events. Spinicaudatan size varies significantly according to faunal association. A forward stepwise regression model suggests that growth responded to population density and diversity: lower densities and higher diversities triggered fast growth, and vice versa. The proposed strong density effect on carapace size has been corroborated by rearing experiments: As for E. middendorfii, natural log regression provided the best fit for the two extant species Eulimnadia texana and Eocyzicus argillaquus. Hence, Eosestheria middendorfii was a tolerant and morphologically variable species adapted to perennial waters and the frequent presence of higher trophic levels. Although there are rare records of extant taxa co-occurring with fish, the described Early Cretaceous environment is commonly not realized by extant Spinicaudata.
Data from: A gravid fossil turtle from the Early Cretaceous reveals a different egg development strategy to that of extant marine turtles
Extant sea turtles develop and lay pliable (flexible) eggs, however, it is unknown if they inherited this reproductive strategy from their closer fossil relatives or corresponds to an evolutionary novelty. Here we describe the first undisputable gravid marine fossil turtle ever found, from the early Cretaceous of Colombia, belonging to Desmatochelys padillai Cadena and Parham, which constitutes a representative of Protostegidae. Using thin sectioning of one the eggs, as well as scanning electron microscopy coupled with elemental characterization, cathodoluminescence, and computer tomography we established that Desmatochelys padillai produced rigid eggs similar to the ones found in some extant and fossil freshwater and terrestrial turtles, and that at least 48 spherical eggs are preserved inside this gravid turtle. We performed also a phylogenetic analysis of several turtle taxa, including some of the extant marine species, plus the information from the gravid specimen of Desmatochelys padillai, and we found more support to previous ideas that egg and eggshell characters lack of strong phylogenetic signal amongst turtle taxa. We suggest that the development of rigid eggs in the marine extinct turtle Desmatochelys padillai resulted as an adaptation for eggs-embryos requirements dictated by the physical attributes of the nesting site
Data from: Early Cretaceous cyclostome bryozoans from the early to middle Albian of the Glen Rose and Walnut formations of Texas, USA
The Glen Rose and Walnut formations of southcentral and northcentral Texas comprise shallow-water carbonates deposited during the late Aptian to middle Albian on a carbonate platform. The formations are famous for their rich fossil faunas. Although bryozoans are absent in late Aptian sediments, they are frequently found encrusting bivalve shells from the early to middle Albian parts of these formations. Here, we describe the cyclostome bryozoan fauna, which includes six species; Stomatopora sp., Oncousoecia khirar n. sp., Reptomultisparsa mclemoreae n. sp., Hyporosopora keera n. sp., Mesonopora bernardwalteri n. sp. and ?Unicavea sp. Most cyclostomes are found encrusting rudist shells from Unit 2 of the Lower Member of the Glen Rose Formation and units 3 and 6 of the Upper Member of the Glen Rose Formation.
Data from: Body shape diversity in Triassic‒Early Cretaceous neopterygian fishes: sustained holostean disparity and predominantly gradual increases in teleost phenotypic variety
Comprising Holostei and Teleostei, the ~32,000 species of neopterygian fishes are anatomically disparate and represent the dominant group of aquatic vertebrates today. However, the pattern by which teleosts rose to represent almost all of this diversity, while their holostean sister group dwindled to 8 extant species and two broad morphologies, is poorly constrained. A geometric morphometric approach was taken to generate a morphospace from over 400 fossil taxa, representing almost all articulated neopterygian taxa known from the first 150 million years—roughly 60%—of history (Triassic‒Early Cretaceous). Patterns of morphospace occupancy and disparity are examined in order to: assess evidence for a phenotypically 'dominant' holostean phase; evaluate whether expansions in teleost phenotypic variety are predominantly abrupt or gradual, including assessment of whether apomorphy-defined teleosts are as morphologically conservative as typically assumed; compare diversification in crown and stem teleosts. The systematic affinities of dapediiforms and pycnodontiforms, two extinct neopterygian clades of uncertain phylogenetic placement, significantly impact patterns of morphological diversification. For instance, alternative placements dictate whether or not holosteans possessed statistically higher disparity than teleosts in the Late Triassic and Jurassic. Despite this ambiguity, all scenarios agree that holosteans do not exhibit a decline in disparity during the Early Triassic‒Early Cretaceous interval, but instead maintain their Toarcian‒Callovian variety until the end of the Early Cretaceous without substantial further expansions. After a conservative Induan‒Carnian phase, teleosts colonize (and persistently occupy) novel regions of morphospace in a predominantly gradual manner until the Hauterivian, after which expansions are rare. Furthermore, apomorphy-defined teleosts possess greater phenotypic variety than typically assumed. Comparison of crown and stem teleost partial disparity indicates that, despite substantial expansion in crown teleosts between the Late Jurassic and earliest Cretaceous, stem teleosts remained important long-term contributors to overall teleost disparity during this time.
Data from: Marine life in a greenhouse world: cephalopod biodiversity and biogeography during the early Late Cretaceous
Two end-member models are proposed to explain marine biotic responses to greenhouse conditions. Global warming and increasing sea level may: (1) promote dispersal of marine species, leading to larger geographic ranges and decreased speciation and biodiversity, or (2) form isolated epicontinental basins that host endemic radiations, leading to smaller geographic ranges and increased speciation and biodiversity. The Cenomanian–Turonian (C–T) interval, marked by greenhouse warming, sea level rise, ocean anoxia, and biotic turnover, presents an opportunity to test these two end-member models. In particular, how cephalopods responded to these global changes has not been clear. A global database of 7,262 cephalopod occurrences was used to evaluate biodiversity changes through the C–T interval. Both species- and genus-level diversity peaked in the Late Cenomanian. The global diversity drop across the C/T boundary was modest; rather, diversity was low during the Middle Cenomanian and Middle Turonian, times of brief cooling. Regional variations in diversity responses may reflect the degree and timing of environmental perturbations within different oceanographic settings. Surprisingly, cephalopod faunas in the European Platform, Western Interior, and South Atlantic all shifted equatorward across the C/T boundary, whereas other regions saw no change in latitudinal distributions. Global generic geographic ranges did not change through the C–T interval, but the percentage of cosmopolitan genera did increase significantly across the C/T, both globally and within the Western Interior and Europe, whereas cosmopolitans dropped in the Pacific and South Atlantic. Neither end-member model for biodiversity change in a greenhouse world is supported for C–T cephalopods, as diversity increased without an associated increase in geographic range. It may be that sea level rise and global warming led to both endemic radiations in epicontinental basins and an increase in cosmopolitan taxa in some regions, demonstrating the importance of combining global and regional scale analyses.
Data from: The plumage and colouration of an enantiornithine bird from the Early Cretaceous of China
Brilliant colour displays and diverse feather morphologies that are often sexual ornaments are common throughout much of extant Avialae. Here we describe a new basal enantiornithine bird specimen recovered from the Early Cretaceous Jiufotang Formation of Liaoning Province in northeastern China. We present new information on the plumage of Bohaiornithidae as well as the first detailed colour reconstruction of an enantiornithine bird. The new specimen retains subadult skeletal characteristics, including periosteal pitting of the long bone epiphyses and unfused elements, while also preserving plumage evidence consistent with sexual maturity at the time of death. Exceptionally-preserved feathers cover the body, including elongate crown feathers, body contour feathers, asymmetrically-veined wing primaries, an alula and two elongate rachis-dominated rectrices that may have been sexual ornaments. The crown, neck, and body contour feathers retain elongate melanosome morphologies associated with weakly iridescent colouration in extant feathers. We provide additional evidence of preserved melanin using Raman spectroscopy; a rapid, non-destructive chemical technique. The new specimen provides data on skeletal ontogeny in the Bohaiornithidae as well as evidence for intraspecific communication functions of plumage.
FIGURE 5 in A new side-necked turtle (Pleurodira, Pelomedusoides) from the Santana Formation (Early Cretaceous), Araripe Basin, Northeastern Brazil
FIGURE 5. Ventral view of Caririemys violetae. Scale: 30 mm. Abbreviations: axi, axillary buttresses; cos, costal plate; ia, iliac articulation; ing, ingunal buttresses; per, peripheral plate; py, pygal plate. Scale: 30 mm.
FIGURE 3 in A new side-necked turtle (Pleurodira, Pelomedusoides) from the Santana Formation (Early Cretaceous), Araripe Basin, Northeastern Brazil
FIGURE 3. Reconstruction of the carapace of Caririemys violetae n. gen., n. sp. (MN 6919–V), dorsal aspect. Abbreviations: cos, costal plate; neu, neural plate; nuc, nuchal plate; per, peripheral plate; py, pygal plate. Scale: 30 mm.
FIGURE 1 in A new side-necked turtle (Pleurodira, Pelomedusoides) from the Santana Formation (Early Cretaceous), Araripe Basin, Northeastern Brazil
FIGURE 1. Map showing location the Araripe Basin and the members that form the Santana Formation. Ages based on Ponte & Ponte Filho (1996).
FIGURE 2 in A review of the brachylepadomorph cirripede genus Pycnolepas, including the first record of an Early Cretaceous species from the Russian Far East *
FIGURE 2. Map showing provenance area in the Khabarovsk region, Russian Far East (inset), and simplified map of the Amur River near Vassa and Irkutskoye, south of Bogorodskoye. Localities 901 and 1024-I are in the same general area, near Vassa, referred to as Vassinskaja protoka.
FIGURE 1 in A review of the brachylepadomorph cirripede genus Pycnolepas, including the first record of an Early Cretaceous species from the Russian Far East *
FIGURE 1. Geographic distribution (solid black dots) of members of the genus Pycnolepas; note the disjunct occurrences of early(?) Aptian and middle Albian species in Antarctica and in the Russian Far East, respectively. Dots for southern Sweden and Belgium/the Netherlands in fact represent more than one species, namely P. ignabergensis + P. bruennichi, and P. bruennichi, P. landenica + P. industriosa, respectively. Pycnolepas orientalis, from an unspecified Upper Cretaceous level in Azerbaijan, is here considered a nomen dubium (see text); P. nov. sp. from the upper Paleocene of Kazakhstan has not yet been described or illustrated.
FIGURE 3 in A review of the brachylepadomorph cirripede genus Pycnolepas, including the first record of an Early Cretaceous species from the Russian Far East *
FIGURE 3. Pycnolepas aff. rigida (J. de C. Sowerby, 1836), all capitular valves from localities 901 and 1024-I, Vassinskaja protoka, southwest of Bogorodskoye, Khabarovsk region, Russian Far East. A, fragmentary right scutum (VSEGEI/CNIGR Museum, no. 58/13062), locality 901, leg. V.D. Ovchinnikov, 1966 (= Sey et al., 2004: pl. 92, fig.15a, b); B, fragmentary right scutum (VESGEI/CNIGR Museum, no. 57/13062), locality 901, leg. V.D. Ovchinnikov, 1966 (= Sey et al., 2004: pl. 92, fig. 14a, b); C, left scutum (VSEGEI/CNIGR Museum, no. 128/13062), locality 1024-I, leg. L.P. Ejkhvald, 2000 (= Sey et al., 2004: pl. 92, fig. 16); D, abraded right scutum (VSEGEI/CNIGR Museum, no. 130/13062), locality 1024-I, leg. L.P. Ejkhvald, 2000; E, fragmentary carina (VSEGEI/CNIGR Museum, no. 129/13062), locality 1024-I, leg. L.P. Ejkhvald, 2000. Scale bars equal 10 mm.
FIGURE 6 in Barrosasaurus casamiquelai gen. et sp. nov., a new titanosaur (Dinosauria, Sauropoda) from the Anacleto Formation (Late Cretaceous: early Campanian) of Sierra Barrosa (Neuquén, Argentina)
FIGURE 6. Barrosasaurus casamiquelai gen. et sp. nov., holotype. Dorsal centra in ventral view: A, MCF-PVPH-447/ 3; B, MCF-PVPH-447/1; MCF-PVPH-447/2. Abbreviation: vk, ventral keel. Scale bar equals 10 cm.
FIGURE 5 in Barrosasaurus casamiquelai gen. et sp. nov., a new titanosaur (Dinosauria, Sauropoda) from the Anacleto Formation (Late Cretaceous: early Campanian) of Sierra Barrosa (Neuquén, Argentina)
FIGURE 5. Barrosasaurus casamiquelai gen. et sp. nov., holotype (MCF-PVPH-447/2). Posterior dorsal (ninth or tenth) vertebra in anterior (A), posterior (B), left (C), and right lateral (D) views. Abbreviations: acpl, anterior centroparapophyseal lamina; alp, aliform process; apcdl, accesory posterior centrodiapophyseal lamina; aspdl, anterior spinodiapophyseal lamina; f, fossa; nc, neural canal; p, pleurocoel; pcdl, posterior centrodiapophyseal lamina; pcpl, posterior centroparapophyseal lamina; podl, postzygodiapophyseal lamina; posl, postspinal lamina; prsl, prespinal lamina; prz, prezygapophysis; pz, postzygapophysis; r, rib; spol, spinoposztzygapophyseal lamina; sprl, spinoprezygapophyseal lamina; tl, transverse lamina. Scale bar equals 10 cm.
FIGURE 2. A in Barrosasaurus casamiquelai gen. et sp. nov., a new titanosaur (Dinosauria, Sauropoda) from the Anacleto Formation (Late Cretaceous: early Campanian) of Sierra Barrosa (Neuquén, Argentina)
FIGURE 2. A) Photograph of the holotype material of Barrosasaurus casamiquelai gen. et sp. nov. during excavation. B) Map showing the original positions of the specimens. The grid is composed of 10 x 10 cm quadrats.
FIGURE 8 in Barrosasaurus casamiquelai gen. et sp. nov., a new titanosaur (Dinosauria, Sauropoda) from the Anacleto Formation (Late Cretaceous: early Campanian) of Sierra Barrosa (Neuquén, Argentina)
FIGURE 8. Comparison among posterior dorsal vertebrae of some selected titanosaurs. A, B, Barrosasaurus casamiquelai gen. et. sp. nov. (holotype, MCF-PVPH-447/2), ninth or tenth dorsal in posterior (A) and right lateral (B) views. C, D, Neuquensaurus australis (MCS-5), dorsal 9? in posterior (C) and right lateral (D) views. E, F, Argyrosaurus superbus (PVL 4628, MACN-CH 217), dorsal 10? in anterior (E) and right lateral (F) views. G, Trigonosaurus pricei (holotype, MCT-1488-R), dorsals 9 and 10 in left lateral view. Scale bar equals 10 cm.
FIGURE 7 in Barrosasaurus casamiquelai gen. et sp. nov., a new titanosaur (Dinosauria, Sauropoda) from the Anacleto Formation (Late Cretaceous: early Campanian) of Sierra Barrosa (Neuquén, Argentina)
FIGURE 7. Comparison of anterior dorsal vertebrae of some selected titanosaurs, in anterior view. A, Barrosasaurus casamiquelai gen. et sp. nov. (holotype, MCF-PVPH-447/3). B, Argentinosaurus huinculensis (holotype, MCF-PVPH- 1). C, Mendozasaurus neguyelap (paratype, IANIGLA-PV 066). Scale bar equals 10 cm.
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Allen Brain Atlas
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Annotated Behaviour and Observability Dataset (ABODe)
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