The earliest herbivorous marine reptile and its remarkable jaw apparatus
Authors:
Chun et al
Abstract:
Newly discovered fossils of the Middle Triassic reptile Atopodentatus unicus call for a radical reassessment of its feeding behavior. The skull displays a pronounced hammerhead shape that was hitherto unknown. The long, straight anterior edges of both upper and lower jaws were lined with batteries of chisel-shaped teeth, whereas the remaining parts of the jaw rami supported densely packed needle-shaped teeth forming a mesh. The evidence indicates a novel feeding mechanism wherein the chisel-shaped teeth were used to scrape algae off the substrate, and the plant matter that was loosened was filtered from the water column through the more posteriorly positioned tooth mesh. This is the oldest record of herbivory within marine reptiles.
As grasses grew more common in Africa, most major mammal groups tried grazing on them at times during the past 4 million years, but some of the animals went extinct or switched back to browsing on trees and shrubs, according to a study led by the University of Utah.
"It's as if in a city, there was a whole new genre of restaurant to try," says geochemist Thure Cerling, first and senior author of the study published today by the journal Proceedings of the National Academy of Sciences. "This is a record of how different mammals responded. And almost all of the mammals did an experiment in eating this new resource: grass."
The experiment peaked about 2 million years ago, says Cerling, a distinguished professor of geology and geophysics. The only major group that still mostly grazes grass is the bovids: cattle, buffalo, sheep, wildebeest, hartebeest and some antelopes such as oryx and waterbucks.
The study also revealed that the present isn't necessarily the key to the past in terms of what animals eat. Today, elephants and spiral-horned antelope (elands, kudus and bushbuck) browse on trees and shrubs, but the study showed that 2 million years ago, African elephants grazed on grass and the antelopes had mixed diets with a lot of grass. Asian elephants, which ate grass and were abundant in Africa 2 million years ago, went extinct in Africa but survive in Asia, where they graze but also browse trees and shrubs.
"That the diet of some of these animals is different from that of the present was a surprise, and shows the importance of challenging one's assumptions when making ecological reconstructions," says study co-author and geologist Frank Brown, dean of the University of Utah's College of Mines and Earth Sciences.
Overall, Cerling and colleagues wrote that the assemblages of grazing, browsing and mixed-diet animals during the past 4 million years "are different from any modern ecosystem in East or Central Africa."
HERBIVOROUS AND DETRITIVOROUS ARTHROPOD TRACE FOSSILS ASSOCIATED WITH SUBHUMID VEGETATION IN THE MIDDLE PENNSYLVANIAN OF SOUTHERN BRITAIN
Authors:
Falcon-Lang et al
Abstract:
We describe plant–arthropod associations from the Middle Pennsylvanian (late Bolsovian–early Asturian) Pennant Sandstone Formation of southern Britain. Our material comprises calcified cordaitaleans and tree-fern axes, preserved in braided channel deposits, and interpreted as remains of subhumid riparian vegetation distinct from that of coeval coal swamps. The first plant–arthropod association, attributed to herbivorous insects, comprises cambial damage to cordaitalean leafy branches, resulting in traumatic wound response. The second and most widespread association, attributable to detritivorous oribatid mites, includes tunnels and galleries containing widely scattered, clustered, or densely packed microcoprolites within the inner root mantle of marattialean tree ferns and cordaitalean trunks and branches. Diameter data for tunnels and microcoprolites are multimodal, recording four or five instars of oribatid mites that parallel instar-based fecal pellet and body lengths in modern taxa. The third association attributed, possibly, to an arthropleurid, comprises a single, very large (19 × 14 mm) coprolite. Included plant fragments support a previous conjecture that arborescent lycopsids formed part of this iconic arthropod's diet. Mucus-lined burrows within the macrocoprolite imply that fecal material was processed by annelids. The high diversity and frequency of plant–arthropod associations are unusual for Mid-Pennsylvanian time, and may reflect previously undetected interactions in those ecosystems that lay outside “coal forest swamps.”
Carnivorous plants catch and digest tiny animals in order and derive benefits for their nutrition. Interestingly the trend towards vegetarianism seems to overcome carnivorous plants as well. The aquatic carnivorous bladderwort, which can be found in many lakes and ponds worldwide, does not only gain profit from eating little animals but also by consuming algae and pollen grains. This results in survival in aquatic habitats where prey animals are rare, and in increased fitness if the animals and algae are caught in a well-balanced diet. An Austrian research group around Marianne Koller-Peroutka and Wolfram Adlassnig published these results in the respected journal Annals of Botany.
The bladderworts (Utricularia) are one of the largest genera in carnivorous plants with over 200 species. Aquatic bladderworts catch their prey with highly sophisticated suction traps consisting of little bladders that produce a hydrostatic under pressure. A valve-like trap door opens upon stimulation and the surrounding water including tiny organism flushes in rapidly within three milliseconds. Once inside the trap, the prey dies of suffocation and is degraded by digestive enzymes. Due to the minerals provided by prey organisms, bladderworts are able to live and propagate even in habitats that are extremely poor in nutrients.
Animal–plant interactions in a Middle Permian permineralised peat of the Bainmedart Coal Measures, Prince Charles Mountains, Antarctica
Authors:
Slater et al
Abstract:
Evidence for invertebrate feeding on glossopterid gymnosperms is documented from Middle Permian silicified peats of the Prince Charles Mountains, Antarctica, in the form of coprolites occurring both free in the peat matrix and clustered within excavations in roots, aerial wood and leaves. Observations of coprolites in thin-sections of the peats and from scanning electron microscopy of examples extracted via bulk maceration reveal nine morphotypes distinguished by size, shape, surface texture and contents. These include coprolites with coarse plant debris, spirally ornamented coprolites, coprolites containing spore/pollen remains and fern sporangia, coprolites within Glossopteris leaves, an ellipsoidal morphotype within a fern sporangium, large isolated coprolites between matted leaves, clustered forms filling galleries inside Vertebraria roots and Australoxylon wood, forms with coarse indeterminate constituents and others with fungal contents. Other faunal evidence is limited to indeterminate arthropod exoskeleton fragments. Collectively, the coprolites within the permineralised peat from the Prince Charles Mountains document the presence of diverse feeding behaviours including stem feeding, sporangial feeding, palynivory, root feeding and mycophagy. The first evidence of invertebrate feeding traces in Vertebraria (glossopterid) roots is identified. These findings indicate that herbivory by invertebrates in the high-latitude Permian forest-mire ecosystems of Antarctica was more intense and diverse than previous studies have reported, and affected all parts of the Glossopteris plant, together with components of associated herbaceous taxa.
Evidence for insect-mediated skeletonization on an extant fern family from the Upper Triassic of China
Authors:
Feng et al
Abstract:
Leaf skeletonization represents a distinctive form of insect feeding behavior. It commonly occurs in angiosperm leaves after their initial appearance during the Early Cretaceous. This type of feeding behavior rarely has been documented in pre-Mesozoic fossils. We describe the earliest evidence of insect-skeletonized leaves of Dictyophyllum nathorstii Zeiller, affiliated with the extant fern family Dipteridaceae in the Late Triassic Yipinglang flora from southwestern China. The skeletonization generally is located adjacent to the pinna rachilla of the distal free portion of the leaf. In the skeletonized area, the interveinal tissue is completely removed, exposing the pinna rachilla, pinnule midveins, and lateral veins. Most nonvascular tissue has been removed between the vascular bundles, the latter forming polygonal meshes of varying size. Our report of insect-mediated skeletonization of fern leaves from southwestern China fills a spatiotemporal gap in the published data on the paleogeographical distribution and stratigraphic occurrence of plant–arthropod associations, and indicates an antagonistic relationship between a fern host and its insect herbivore.
The captorhinid reptile Captorhinikos valensis from the lower Permian Vale Formation of Texas, and the evolution of herbivory in eureptiles
Authors:
Modesto et al
Abstract:
Captorhinikos valensis is a poorly known, multiple-tooth-rowed captorhinid reptile from the Lower Permian Vale Formation of Texas. Our reappraisal of C. valensis reveals it to be a small moradisaurine, exhibiting a maximum of five rows of bullet-shaped teeth in the multiple-rowed region of both the maxilla and the dentary. The slightly radiating organization of the tooth rows distinguishes C. valensis from the parallel arrangement of the tooth rows exhibited by all other moradisaurines. Captorhinikos valensis is also distinguishable from the coeval moradisaurine Labidosaurikos meachami by a more conspicuously denticulated, broader, ‘U’-shaped transverse flange of the pterygoid, a plesiomorphic morphology shared with the large, single-rowed captorhinid Labidosaurus hamatus. Postcranial information is limited to two short series of presacral vertebrae not associated with the cranial materials; open neurocentral sutures are present in one specimen, indicating immaturity at death. We investigated the relationships of C. valensis to other captorhinids by adding it to the data matrix of a previously published analysis that included several moradisaurine captorhinids. A branch-and-bound PAUP analysis discovered a single optimal tree. Whereas a previous analysis of captorhinid interrelationships found the (undifferentiated) genus Captorhinikos to fall outside of a clade composed of L. hamatus and the large moradisaurines, our analysis recovered C. valensis in a clade with the genera Labidosaurikos, Gansurhinus, Moradisaurus, and Rothianiscus (i.e., Moradisaurinae sensu stricto), and Captorhinikos chozaensis as the sister species of a clade that includes L. hamatus and Moradisaurinae s.s.; Captorhinikos chozaensis is no longer classifiable as a moradisaurine (according to our phylogenetic definition for the group), and should be assigned to a new genus. Stratigraphic calibration of our captorhinid phylogeny indicates that moradisaurines evolved by the middle Kungurian (middle Leonardian).
A new sphenodontian (Lepidosauria: Rhynchocephalia) from the Late Triassic of Argentina and the early origin of the herbivore opisthodontians
Authors:
Martinez et al
Abstract:
Sphenodontians were a successful group of rhynchocephalian reptiles that dominated the fossil record of Lepidosauria during the Triassic and Jurassic. Although evidence of extinction is seen at the end of the Laurasian Early Cretaceous, they appeared to remain numerically abundant in South America until the end of the period. Most of the known Late Cretaceous record in South America is composed of opisthodontians, the herbivorous branch of Sphenodontia, whose oldest members were until recently reported to be from the Kimmeridgian–Tithonian (Late Jurassic). Here, we report a new sphenodontian, Sphenotitan leyesi gen. et sp. nov., collected from the Upper Triassic Quebrada del Barro Formation of northwestern Argentina. Phylogenetic analysis identifies Sphenotitan as a basal member of Opisthodontia, extending the known record of opisthodontians and the origin of herbivory in this group by 50 Myr.
