Not Triassic but too potentially cool to pass up....
O'Keefe, F. R., and L. M. Chiappe. 2011. Viviparity and K-Selected Life History in a Mesozoic Marine Plesiosaur (Reptilia, Sauropterygia). Science 333:870-873. DOI: 10.1126/science.1205689
Abstract - Viviparity is known in several clades of Mesozoic aquatic reptiles, but evidence for it is lacking in the Plesiosauria. Here, we report a Late Cretaceous plesiosaur fossil consisting of a fetus preserved within an adult of the same taxon. We interpret this occurrence as a gravid female and unborn young and hence as definitive evidence for plesiosaur viviparity. Quantitative analysis indicates that plesiosaurs gave birth to large, probably single progeny. The combination of viviparity, large offspring size, and small brood number differs markedly from the pattern seen in other marine reptiles but does resemble the K-selected strategy of all extant marine mammals and a few extant lizards. Plesiosaurs may have shared other life history traits with these clades, such as sociality and maternal care.
Showing posts with label behavior. Show all posts
Showing posts with label behavior. Show all posts
Possible Evidence for Archosaur Predation on Horseshoe Crabs
Diedrich, C. G. 2011. Middle Triassic horseshoe crab reproduction areas on intertidal flats of Europe with evidence of predation by archosaurs. Biological Journal of the Linnean Society103: 76–105. doi: 10.1111/j.1095-8312.2011.01635.x
Abstract - A systematically excavated track site in a 243.5 Myr old Middle Triassic (Karlstadt Formation, Pelsonian, middle Anisian) intertidal carbonate mud-flat palaeoenvironment at Bernburg (Saxony-Anhalt, central Germany) has revealed extensive horseshoe crab trackways attributable to the Kouphichnium Nopsca, 1923 ichnogenus. The exposed track bed of a Germanic Basin-wide spanned intertidal megatrack site is a mud-cracked biolaminate surface on which detailed tracks have been preserved because of rapid drying and cementation as a result of high temperatures, followed by rapid covering with a protective layer of arenitic storm or tsunami sediments. The different trackway types and their orientations have allowed a tidal sequence to be reconstructed, with the initial appearance of swimming horseshoe crabs followed by half-swimming/half-hopping limulids under the shallowest water conditions. The Bernburg trackways, which have mapped lengths of up to 40 m, were all produced by adult animals and exhibit a variety of shapes and patterns that reflect a range of subaquatic locomotion behaviour more typical of mating than of feeding activities. The closest match to the proportions and dimensions of the horseshoe crab tracks at Bernburg is provided by the largest known Middle Triassic limulid Tachypleus gadeai, which is known from the north-western Tethys in Spain. The horseshoe crab body fossils recognized in the German Mesozoic intertidal zones, instead, are from juveniles. The uniformly adult size indicated by the trackways therefore suggests that they may record the oldest intertidal reproductive zones of horseshoe crabs known from anywhere in the world, with the track-makers having possibly migrated thousands of kilometres from shallow marine areas of the north-western Tethys to reproduce in the intertidal palaeoenvironments of the Germanic Basin. Chirotherium trackways of large thecodont archosaurs also appeared on these flats where they appear to have fed on the limulids. With the tidal ebb, smaller reptiles such as Macrocnemus (Rhynchosauroides trackways) appeared on the dry intertidal flats, probably feeding on marine organisms and possibly also on horseshoe crab eggs.
Abstract - A systematically excavated track site in a 243.5 Myr old Middle Triassic (Karlstadt Formation, Pelsonian, middle Anisian) intertidal carbonate mud-flat palaeoenvironment at Bernburg (Saxony-Anhalt, central Germany) has revealed extensive horseshoe crab trackways attributable to the Kouphichnium Nopsca, 1923 ichnogenus. The exposed track bed of a Germanic Basin-wide spanned intertidal megatrack site is a mud-cracked biolaminate surface on which detailed tracks have been preserved because of rapid drying and cementation as a result of high temperatures, followed by rapid covering with a protective layer of arenitic storm or tsunami sediments. The different trackway types and their orientations have allowed a tidal sequence to be reconstructed, with the initial appearance of swimming horseshoe crabs followed by half-swimming/half-hopping limulids under the shallowest water conditions. The Bernburg trackways, which have mapped lengths of up to 40 m, were all produced by adult animals and exhibit a variety of shapes and patterns that reflect a range of subaquatic locomotion behaviour more typical of mating than of feeding activities. The closest match to the proportions and dimensions of the horseshoe crab tracks at Bernburg is provided by the largest known Middle Triassic limulid Tachypleus gadeai, which is known from the north-western Tethys in Spain. The horseshoe crab body fossils recognized in the German Mesozoic intertidal zones, instead, are from juveniles. The uniformly adult size indicated by the trackways therefore suggests that they may record the oldest intertidal reproductive zones of horseshoe crabs known from anywhere in the world, with the track-makers having possibly migrated thousands of kilometres from shallow marine areas of the north-western Tethys to reproduce in the intertidal palaeoenvironments of the Germanic Basin. Chirotherium trackways of large thecodont archosaurs also appeared on these flats where they appear to have fed on the limulids. With the tidal ebb, smaller reptiles such as Macrocnemus (Rhynchosauroides trackways) appeared on the dry intertidal flats, probably feeding on marine organisms and possibly also on horseshoe crab eggs.
New Triassic Terror: Rauisuchian Packs, New Evidence from the Middle Triassic of Brazil
I'm glad everyone enjoyed my April Fools joke; however, the Triassic is here to stay and especially Triassic vertebrate paleontology because the month of April is going to see the publication of numerous new papers on the subject. In fact, April 2011 has the possibility of being the best month ever for Triassic VP, especially archosaurs. We'll revisit this at the end of the month and see if this is true.
The first paper of April 2011 describes the recovery of nine articulated and associated rauisuchian skeletons from the Middle Triassic of Brazil. They have been assigned to a new Prestosuchus-like taxon named Decuriasuchus quartacolonia ("legion of ten crocodile from Quarta Colonia"). The material looks amazing and finds like this are extremely rare in the Triassic so I hope that a full description of the material will be forthcoming.
The phylogenetic analysis utilizes the dataset of Brusatte et al. (2010) and recovers a paraphyletic "rauisuchidae" with Decuriasuchus nesting with Prestosuchus and Batrachotomus; however, the paper and supplemental materials do discuss problems with the existing dataset and therefore these results should be considered very tentative.
One interesting point of the paper is the potential social implications of finding nine rauisuchians clustered together in a single spot. Franca et al., argue that the taphomomy of the site precludes that this is not a time averaged assemblage and instead it appears that these animals (all adults) congregated for some reason before dying. Whether the group was assembled and killed by a sudden catastrophy (e.g, flash flood) or accumulated and died because of another type of event (e.g., drought) is undeterminable with the current evidence, but in either case this would call for a certain degree of interaction between these predators. Modern crocodilians congregate in large number for various reasons, but mainly for feeding and in some cases have been reported to work together to herd fish. Thus, the circumstantial evidence from this new find may suggest that rauisuchians may also have worked together in some cases for hunting strategies. As stated by Franca et al in their concluding sentence, this would represent "the earliest evidence of possible group behavior among archosaurs". I personally would think that a hunting pack of large rauisuchians would be quite formidable, but then again this Brazilian group appears to have lacked invulnerability. Furthermore this would be extremely difficult to support with the evidence.
Note: The Revueltosaurus bonebed in Petrified Forest National Park is a monotypic assemblage of at least a dozen individuals (all of the same size and situated on a levee adjacent to the river channel).
Franca, M. A. G., Ferigolo, J., and M. C. Langer. 2011. Associated skeletons of a new middle Triassic “Rauisuchia” from Brazil. Naturwissenschaften (online first) DOI: 10.1007/s00114-011-0782-3
Abstract - For more than 30 million years, in early Mesozoic Pangea, “rauisuchian” archosaurs were the apex predators in most terrestrial ecosystems, but their biology and evolutionary history remain poorly understood. We describe a new “rauisuchian” based on ten individuals found in a single locality from the Middle Triassic (Ladinian) Santa Maria Formation of southern Brazil. Nine articulated and associated skeletons were discovered, three of which have nearly complete skulls. Along with sedimentological and taphonomic data, this suggests that those highly successful predators exhibited some kind of intraspecific interaction. Other monotaxic assemblages of Triassic archosaurs are Late Triassic (Norian-Rhaetian) in age, approximately 10 million years younger than the material described here. Indeed, the studied assemblage may represent the earliest evidence of gregariousness among archosaurs, adding to our knowledge on the origin of a behavior pattern typical of extant taxa.
The first paper of April 2011 describes the recovery of nine articulated and associated rauisuchian skeletons from the Middle Triassic of Brazil. They have been assigned to a new Prestosuchus-like taxon named Decuriasuchus quartacolonia ("legion of ten crocodile from Quarta Colonia"). The material looks amazing and finds like this are extremely rare in the Triassic so I hope that a full description of the material will be forthcoming.
The phylogenetic analysis utilizes the dataset of Brusatte et al. (2010) and recovers a paraphyletic "rauisuchidae" with Decuriasuchus nesting with Prestosuchus and Batrachotomus; however, the paper and supplemental materials do discuss problems with the existing dataset and therefore these results should be considered very tentative.
One interesting point of the paper is the potential social implications of finding nine rauisuchians clustered together in a single spot. Franca et al., argue that the taphomomy of the site precludes that this is not a time averaged assemblage and instead it appears that these animals (all adults) congregated for some reason before dying. Whether the group was assembled and killed by a sudden catastrophy (e.g, flash flood) or accumulated and died because of another type of event (e.g., drought) is undeterminable with the current evidence, but in either case this would call for a certain degree of interaction between these predators. Modern crocodilians congregate in large number for various reasons, but mainly for feeding and in some cases have been reported to work together to herd fish. Thus, the circumstantial evidence from this new find may suggest that rauisuchians may also have worked together in some cases for hunting strategies. As stated by Franca et al in their concluding sentence, this would represent "the earliest evidence of possible group behavior among archosaurs". I personally would think that a hunting pack of large rauisuchians would be quite formidable, but then again this Brazilian group appears to have lacked invulnerability. Furthermore this would be extremely difficult to support with the evidence.
Note: The Revueltosaurus bonebed in Petrified Forest National Park is a monotypic assemblage of at least a dozen individuals (all of the same size and situated on a levee adjacent to the river channel).
Franca, M. A. G., Ferigolo, J., and M. C. Langer. 2011. Associated skeletons of a new middle Triassic “Rauisuchia” from Brazil. Naturwissenschaften (online first) DOI: 10.1007/s00114-011-0782-3
Abstract - For more than 30 million years, in early Mesozoic Pangea, “rauisuchian” archosaurs were the apex predators in most terrestrial ecosystems, but their biology and evolutionary history remain poorly understood. We describe a new “rauisuchian” based on ten individuals found in a single locality from the Middle Triassic (Ladinian) Santa Maria Formation of southern Brazil. Nine articulated and associated skeletons were discovered, three of which have nearly complete skulls. Along with sedimentological and taphonomic data, this suggests that those highly successful predators exhibited some kind of intraspecific interaction. Other monotaxic assemblages of Triassic archosaurs are Late Triassic (Norian-Rhaetian) in age, approximately 10 million years younger than the material described here. Indeed, the studied assemblage may represent the earliest evidence of gregariousness among archosaurs, adding to our knowledge on the origin of a behavior pattern typical of extant taxa.
New in Science - Unidirectional Airflow in the Lungs of Alligators
I have not seen this paper yet, but the implications are really cool. Thanks to Andy Farke for sharing the abstract.
Farmer, C. G., and K. Sanders. 2010. Unidirectional airflow in the lungs of alligators. Science 327(5963):338-340. DOI: 10.1126/science.1180219
Abstract: The lungs of birds move air in only one direction during both inspiration and expiration through most of the tubular gas-exchanging bronchi (parabronchi), whereas in the lungs of mammals and presumably other vertebrates, air moves tidally into and out of terminal gas-exchange structures, which are cul-de-sacs. Unidirectional flow
purportedly depends on bellowslike ventilation by air sacs and may have evolved to meet the high aerobic demands of sustained flight. Here, we show that air flows unidirectionally through parabronchi in the lungs of the American alligator, an amphibious ectotherm without air sacs, which suggests that this pattern dates back to the basal archosaurs of the Triassic and may have been present in their nondinosaur descendants (phytosaurs, aetosaurs, rauisuchians,crocodylomorphs, and pterosaurs) as well as in dinosaurs.
Farmer, C. G., and K. Sanders. 2010. Unidirectional airflow in the lungs of alligators. Science 327(5963):338-340. DOI: 10.1126/science.1180219
Abstract: The lungs of birds move air in only one direction during both inspiration and expiration through most of the tubular gas-exchanging bronchi (parabronchi), whereas in the lungs of mammals and presumably other vertebrates, air moves tidally into and out of terminal gas-exchange structures, which are cul-de-sacs. Unidirectional flow
purportedly depends on bellowslike ventilation by air sacs and may have evolved to meet the high aerobic demands of sustained flight. Here, we show that air flows unidirectionally through parabronchi in the lungs of the American alligator, an amphibious ectotherm without air sacs, which suggests that this pattern dates back to the basal archosaurs of the Triassic and may have been present in their nondinosaur descendants (phytosaurs, aetosaurs, rauisuchians,crocodylomorphs, and pterosaurs) as well as in dinosaurs.
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