Defining the Bemaraha megatracksite: an update on dinosaur ichnology in Madagascar

The Bemaraha Formation preserves a unique and abundant record of dinosaur footprints, the only occurrence of this type known from Madagascar. Theropod and sauropod tracks occur in Middle Jurassic strata and form an important record from this otherwise poorly documented time interval. Here we report on 18 new tracksites, raising the total number of known localities in the Bemaraha to 31. The majority of these sites occur at a same stratigraphic level that can be traced over an area of at least 30 km2, which makes it one of the most laterally extensive occurrences of dinosaur tracks on record in the southern hemisphere. Dinosaur tracks are restricted to a few bedding surfaces representing times of sea-level lowstand within a normally marine environment. Theropod tracks are by far more abundant than sauropod tracks and typically are oriented towards the palaeocoastline. This pattern is interpreted as evidence of a short-scale migration between feeding and resting grounds. The Bemaraha Formation thus allows a rare glimpse into dinosaur behaviour in a marginal marine environment of Jurassic age.

Enigmatic tracks of solitary sauropods roaming an extensive lacustrine megatracksite in Iberia

Sauropod remains are abundant on the Iberian Peninsula across the Jurassic-Cretaceous transition. Where the osteological record shows a high diversity of this kind of dinosaur, the ichnological findings are mainly limited to sauropod tracks characterized by kidney-shaped manus (with or without pollex impressions) and pes impressions with three claw imprints oriented laterally. Here, we present a new sauropod ichnotaxon, Iniestapodus burgensis, found at several exposures within the Las Sereas megatracksite (Burgos, Spain). These are preserved within lacustrine limestone strata of the Rupelo Formation (Tithonian–Berriasian). Iniestapodus burgensis is characterized by: semicircular manus tracks with small pollex impressions; unusual tetradactyl pes tracks with evidence of four claws oriented anteriorly (I–II) and laterally (III–IV), of variable sizes (short claw I and IV impressions, claw II and III being the largest). The combination of features and comparison with the osteological record allows us to propose a non-titanosaurian titanosauriform as a possible trackmaker. All the Iniestapodus tracks are represented by at least two different size classes of small and medium-sized individuals, and their trackways show different multidirectional orientations. The paleoenvironmental and paleoecological data suggest that Iniestapodus trackmakers were solitary individuals, likely representing different age classes, that crossed and used the Las Sereas shallow lacustrine-palustrine areas as their preferred habitat.

A reevaluation of the Late Jurassic dinosaur tracksite Barkhausen (Wiehengebirge, Northern Germany)

A restudy of the Barkhausen dinosaur tracksite shows that the track-bearing surface reveals considerably more detail than previously indicated, and a new map is presented, showing the trackways of nine sauropods, traveling north, possibly as a group. These are among the smallest sauropod tracks recorded in Europe. There is also evidence of two large theropods crossing the area, one moving to the south and the other to the west. Evidence of at least three other sauropods is registered in the form of isolated manus traces that represent larger individuals. Previous interpretations inferred that sauropod trackways trended south, and therefore suggested a predator chasing its prey as in the purported but controversial attack scenario claimed for the famous Paluxy River site in Texas. Based on the present study, this scenario is no longer tenable for the Barkhausen tracksite. The description of Elephantopoides barkhausensis (Kaever and Lapparent, 1974) shows that it represents a moderately wide gauge, but small manus sauropod and can be assigned under the ichnofamily label Parabrontopodidae. E. barkhausensis as originally defined was a nomen dubium, but it has since been re-described semi-formally, without renaming, we emend the description and assigned them to the ichnotaxon Parabrontopodus barkhausensis comb. nov. These tracks could have been produced by the small sauropod dinosaur taxon Europasaurus. The problematic ichnotaxon Megalosauropus teutonicus (Kaever and Lapparent, 1974), which represents a large three-toed theropod, is assigned to the recently described ichnogenus Jurabrontes from the Late Kimmeridgian of the Swiss Jura mountains as Jurabrontes teutonicus comb. nov. Furthermore, we attribute the theropod tracks from the time equivalent Langenberg quarry to the same ichnotaxon.

A diverse Late Cretaceous vertebrate tracksite from the Winton Formation of Queensland, Australia

The Upper Cretaceous ‘upper’ Winton Formation of Queensland, Australia is world famous for hosting Dinosaur Stampede National Monument at Lark Quarry Conservation Park, a somewhat controversial tracksite that preserves thousands of tridactyl dinosaur tracks attributed to ornithopods and theropods. Herein, we describe the Snake Creek Tracksite, a new vertebrate ichnoassemblage from the ‘upper’ Winton Formation, originally situated on Karoola Station but now relocated to the Australian Age of Dinosaurs Museum of Natural History. This site preserves the first sauropod tracks reported from eastern Australia, a small number of theropod and ornithopod tracks, the first fossilised crocodyliform and ?turtle tracks reported from Australia, and possible lungfish and actinopterygian feeding traces. The sauropod trackways are wide-gauge, with manus tracks bearing an ungual impression on digit I, and anteriorly tapered pes tracks with straight or concave forward posterior margins. These tracks support the hypothesis that at least one sauropod taxon from the ‘upper’ Winton Formation retained a pollex claw (previously hypothesised for Diamantinasaurus matildae based on body fossils). Many of the crocodyliform trackways indicate underwater walking. The Snake Creek Tracksite reconciles the sauropod-, crocodyliform-, turtle-, and lungfish-dominated body fossil record of the ‘upper’ Winton Formation with its heretofore ornithopod- and theropod-dominated ichnofossil record.

Lower Cretaceous Dinosaur Trackways Exposed by Water Erosion in Sichuan Province, China

A newly discovered saurischian dominated tracksite in the Lower Cretaceous Jiaguan Formation in southeastern Sichuan province reveals 13 sauropod trackway segments representing ichnogenus Brontopodus and three theropod trackways. This is a typical Type 1 Jiaguan Formation deposit dominated by tetrapod tracks with no significant tetrapod body fossils. The tracks occur in a river channel exposure of feldspathic quartz sandstone about 20–25 m wide and ~ 60 m long. The trackways are exposed on both banks but eroded away in the central channel area. The sauropod tracks represent relatively small animals with pes print lengths ranging from 24.5 cm to 33.9 cm. The theropod trackways include a large example (footprint length 46.5 cm with metatarsal traces) and two smaller parallel trackways with footprint lengths less than 20 cm. The author also discussed the erosion of tracks and trackways by water erosion, especially their morphological changes.

New Late Cretaceous (Coniacian) sauropod tracks from Hvar Island, Croatia

In June 2017 a new sauropod trackway locality was discovered in the central part of the Adriatic–Dinaric Carbonate Platform (ADCP), on the island of Hvar (Croatia). The track site is situated on the northern shore of the western edge (Pelegrin) of the island in the upper Turonian – lower Coniacian limestone series. The track site contains altogether 13 footprints arranged in four possible trackways. The largest footprints have a diameter up to 80 cm. In some places the limestone surface is strongly karstified and the tracks are partly eroded, which has certainly modified the original shape and size of the footprints. Microfossil assemblage from the track-bearing beds suggest an early Coniacian age for the tracks. The new trackways on Hvar Island further strengthen the earlier hypothesis that sauropods were present in the western Tethyan archipelago during the late Cenomanian–late Campanian period. In addition, the new tracks, together with those from the Žukova Cove of Hvar, represent two, possibly slightly different stratigraphic horizons close to the Turonian–Coniacian boundary, and suggest that the occurrence of sauropods on the ADCP and possibly also on other parts of the Apulian microplate was not accidental, but rather periodical and more frequent than previously thought.