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Drone footage of a large American crocodile bottom walking in shallow coastal water off Costa Rica was used to estimate oblique pace and stride lengths and pace angulations from autopodial touchdowns. The crocodile's pes stride lengths were longer but more variable than expected for an individual of comparable size high-walking on land, due in part to punting locomotion, but also to wave action moving the reptile's body. Pace angulations were also larger than expectations for a crocodile high walking on land. These features are also seen in fossil trackways, suggesting that trackways ascribed to “swimming” crocodylomorphs might better be characterized as made by bottom walking and punting reptiles.
Pterosaur remains are exceptionally rare in the Late Cretaceous marine chalks of Alabama and the few specimens found are typically very fragmentary. We report the occurrence of a metacarpal of Pteranodon cf. longiceps from the Mooreville Chalk (Campanian, 83 million years old) of Dallas County, Alabama. The Pteranodon specimen exhibits serrated teeth marks on the surface of the bone and a second set of larger, unserrated teeth marks unlike those of any contemporary shark species. These feeding traces compare favorably with the tooth spacing and morphology of Squalicorax kaupi, and a small to moderate-sized saurodontid fish, such as Saurodon or Saurocephalus, respectively. In both instances, feeding traces appear to be scavenging events due to the lack of any healing or bone remodeling. During the Campanian, Dallas County, Alabama, was a shallow-marine environment comprising part of the Mississippi Embayment. It is hypothesized that the specimen represents a pterosaur that either fell into marine waters or was washed out from nearshore areas and then scavenged by both a chondrichthyan and osteichthyan. This type of scavenging behavior has been recorded on other taxonomic groups from Alabama during the Late Cretaceous. However, the fragile, hollow bones of pterosaurs make their preservation rare.
The upper Viséan–lower Serpukhovian Roque Redonde Formation in the southern part of the Montagne Noire, SW France, contains carbonate mounds with predominant micropeloidal facies tens of meters thick representing paleotopographic highs. Calcareous green algae, including representatives of the Dasycladales and Bryopsidales, are relatively common within the mounds (varying in percentages from 1% to 15% of the components, exceptionally reaching up to 40%). Six morphological types of algal remains are recognized within the mounds, and represented by (1) fragmented material, (2) discrete segments, (3) semi-articulated elements, (4) articulated elements, (5) stacked blades, and (6) bushes. Analysis of their preservation state suggests that they mostly constitute autochthonous or parautochthonous assemblages, which were living during the growth of the predominant micropeloidal/clotted fabrics of the carbonate mounds. As such, the carbonate mounds in the Roque Redonde Formation would have developed in an outer platform setting under dysphotic-euphotic conditions. Green algae in the carbonate mounds of the Mississippian confirm that they do not have analogs within the modern deep-water/bathyal carbonate mounds. The abundant green algae in the Montagne Noire is an exceptional case for any geological time period.
Environmental changes within a Neogene coastal dune system are recorded by endobenthic unioniform bivalves that lived in muddy or sandy interdune pond sediments. These bivalves were suspension-filter feeders that formed dense, almost monospecific communities in the wet-interdune deposits of the continental intervals of the Río Negro Formation (late Miocene–early Pliocene). Activity of unioniform bivalves appears to be related to sediment type; resting and locomotion traces dominate in the muddy heterolithic facies, whereas equilibrium/escape structures prevail in the sand-dominated heterolithic facies. These traces characterize two scenarios of the wet-interdune development. First, during high and/or relatively stable water levels, bivalves colonized the muddy bottom and produced resting and locomotion traces. When water level dropped due to desiccation, biogenic structures were impacted by the formation of mud cracks and subsequently covered by sand delivered by migrating dunes. Second, in spite of dune migration, some interdune areas remained wet or flooded and, in response to sediment aggradation, the bivalves produced equilibrium or escape structures, depending on the thickness of eolian sand cover. Only the integration of ichnologic and sedimentologic observations allows deciphering the evolution of the Neogene wet-interdune system in such a detail.