Vertebrate Ichnology

An uncommon trackway of a seabird consisting of impressions of the right foot accompanied at the left side at the supposed position of the foot only by holes was produced by a gull having two legs, but only one foot. Foot size and stride are typical of an adult herring gull. The stride is unequal between right-left and left-right impression by »15% as the digitigrade producer experienced redistribution of load due to the missing foot. Tracks of disabled seabirds are underrepresented in reports of both modern settings as well as the fossil record when compared with modern observations. In present time, about 2% of the seabirds have injured feet or legs. Today, however,
injuries of seabirds might have increased due to human fishery activities. Actual observations show that fossilisation of such trackways is favoured by microbes preferentially growing in the impressions that are moist for a prolonged period of time.

Most commonly used features in fossil vertebrate burrow descriptions are not directly related to tracemaker morphology. The general form of vertebrate burrows reflects behaviour and ecology (colonial or solitary; subterranean or surface-dwelling; hibernating or not) that can be found in unrelated and morphologically distinct groups. Burrow diameter is not directly related to morphology but only gives an approximate size range. In contrast, bioglyphs (surface marking) are directly linked to the morphology of appendages and other body parts. In particular, claw marks represent trajectories of digging movements. Although trajectories themselves are often taxon-specific, they can be used to make only limited inferences about tracemaker morphology, because similarly oriented digging strokes can be produced by forelimbs with different proportions. This study suggests a method for inferring the length of forelimb elements from one feature of claw marks, the radius of curvature and its variation. The forelimb can be represented as a kinematic chain with three or four links (Fig. 1). The trajectories produced by movements at each joint are arcs with the radius of curvature corresponding to the distance between the joint and the tip of the claw. The trajectory described by the claws during digging depends on the resistance of the substrate which, in turn, varies with the angle of attack (Fig. 2, 3). The variation of the radius of curvature within a single claw-mark reflects changing proportions between movements at several joints. A single burrow can contain hundreds of claw marks that represent a sufficient sample to make conclusions about forelimb proportions.

For more than 70 years unusual sauropod trackways have played a pivotal role in debates about the swimming ability of sauropods. Most claims that sauropods could swim have been based on manus-only or manus-dominated trackways. However none of these incomplete trackways has been entirely convincing, and most have proved to be taphonomic artifacts, either undertracks or the result of differential depth of penetration of manus and pes tracks, but otherwise showed the typical pattern of normal walking trackways. Here we report an assemblage of unusual sauropod tracks from the Lower Cretaceous Hekou Group of Gansu Province, northern China, characterized by the preservation of only the pes claw traces, that we interpret as having been left by walking, not buoyant or swimming, individuals. They are interpreted as the result of animals moving on a soft mud-silt substrate, projecting their claws deeply to register their traces on an underlying sand layer where they gained more grip during pr...

The Pie de Vaca locality in the State of Puebla stands out for its important abundance of fossil mammal footprints, among them, the most representatives have been referred to camelids and felids. The purpose of the present study was the formal characterization of this set of footprints and comment on some paleobiological aspects related to their size, speed, and mode of progression of the track-makers. The sample consists of 233 footprints including 154 referable to nine trackways produced by camelids and 79 referable to three trackways produced by felids. The characterization of the tracks was made by comparing their size and morphology with others produced by fossil and recent taxa. The impressions of camelids, based on their shape and size, were designated to the icnospecies Lamaichnum guanicoe because they show the typical morphological pattern of this group of artiodactyls. It is suggested that they were produced by some member of the genus Hemiauchenia, which corresponds to the most common camelid of the Late Cenozoic of Mexico. On the other hand, the tracks of felids were only referred to the mor-phofamily Felipedidae due to the bad preservation of its ichnotaxonomic characters; however, being larger than traces of the ichnogenera Felipeda, Pycnodactylopus, Pumaeichnum and Mitsupes, it is suggested that they were produced by some form of medium to large size, a machairodontid or a pantherine, for instance. The mode of progression of both producers corresponds to that of relatively fast walking organisms that move at a speed lower than 4 m/s. The direction and number of individuals of camelids trackways, are indicative of gregarious behavior, probably associated with a certain social organization. In the case of felids, solitary or couple behavior is proposed.

Camel footprints have a well preserved
record in Neogene strata from North America, including Mexico, however their Paleogene record is much less known. Here, we describe the oldest camel footprints from Mexico, located in the outskirts of Tezoatlán de Segura y Luna, northwestern
Oaxaca, southern Mexico. The camel footprints are preserved as concave epirelief in fine-grained tuffaceous sandstone of the late Eocene-early Oligocene Huajuapan Formation. These footprints display the diagnostic features of Lamaichnum guanicoe, such as bidigital tracks with pointed anterior ends and rounded posterior ends, with digit impressions that do not converge anteriorly and footprints that have digit imprints connected. Potential track makers include Paratylopus, Paralabis and Pseudolabis. The concave axial surface and nail imprints of the Oaxacan footprints, indicate that the track makers shared some anatomical foot features with extant camels, suggesting
that some characteristics of the peculiar camel foot had already evolved by the late Eocene-early Oligocene.

In this work, we report the occurrence of proboscidean and canid footprints in the Sardinian fossil record. The ichnofossils are assigned to Proboscipeda panfamilia McNeil, Hills, Tolman and Kooyman, 2007, and Canipeda isp. The studied footprints are preserved in highly consolidated aeolian deposits from the Pleistocene of Funtana Morimenta and Porto Paglia areas (Gonnesa, southwestern Sardinia, Italy). The recovered mammoth ichnofossils are represented by isolated manus-pes couples preserved as hyporeliefs and/or epireliefs. Furthermore, other footprints were observed in situ.

Swim tracks have long been a subject of controversy because they often exhibit incomplete or irregular morphologies. This morphological variation is a result of the highly variable conditions under which they are supposed to have formed; by buoyant/bottom-walking animals in subaqueous environments. The discovery of abundant swim track sites in the Lower Triassic Moenkopi Formation of Utah raises questions about the processes and factors controlling swim track preservation and the spaciotemporal distribution of localities. Despite a growing literature that is beginning to officially recognize swim tracks as distinct from other vertebrate traces, standardized and quantitative methods for describing and analyzing them have yet to be implemented. The Torrey Member of the Moenkopi Formation was deposited under marine deltaic conditions and shows a pervasive lack of bioturbation. This phenomenon is observed in modern brackish environments where frequent salinity and temperature fluctuations create a stressful environment that keeps biological diversity low. In the case of Lower Triassic deposits such as the Moenkopi, the effect may have been exacerbated due to delayed ecologic recovery following the end-Permian mass extinction. These unique factors (stressful environments coupled with delayed recovery) have been hypothesized to be responsible for producing widespread unmixed, firmground substrates ideal for registering and maintaining detailed subaqueous traces. The deposition of heterolithic bedding in certain environments (e.g., deltas and oxbow lakes) increases the subsequent preservation potential of these traces. Thus, Lower Triassic deltaic deposits (e.g., Moenkopi) contain a disproportionately large amount of swim tracks compared to older or younger formations. To begin investigating potential patterns in global swim track occurrences, I have compiled a database of global swim track occurrences with information about location, formation, age, preservation, paleoenvironment, ichnotaxonomy, specimen numbers, and proposed trackmakers. This database, originally comprising 143 tracksites, was first published in Geology nearly 3 years ago. It has since grown to over 180 individual sites. The data are normalized to account for epoch duration (worldwide) and outcrop area (North American sites only). Preliminary results from this large sample suggest that patterns in the preservation and spaciotemporal distribution of swim tracks are real and worth investigating. 83% of swim tracks localities are found in terrestrial paleoenvironments and 43% of localities are interpreted as either lacustrine or marine deltaic/estuarine. Marine deltaic sites make up 29% of all swim track localities while lacustrine and floodplain deposits comprise 12% and 13%, respectively. 68% of swim track localities preserve tracks exclusively as natural casts (convex hyporelief). To avoid confusion and maintain consistency in the literature, a standardized terminology distinct from that used for terrestrial tracks needs to be developed and employed for describing swim tracks. The terminology proposed by McAllister in 1989, in which the terms footmark, footmarks, and traceway are subaqueous correlates to the terms track, tracks, and trackway, is a

The Late Carboniferous Souss Basin of south-central Morocco exhibits an approximately 1,800 m thick succession of fluvial and lacustrine deposits that have yielded diverse fossil remains of plants, insects, conchostracans, ostracods, jellyfish, fishes, and few tetrapod footprints. Recent exploration of ichnofossils of the Souss Basin led to the discovery of several trampled surfaces including tetrapod footprints assigned to the plexus Batrachichnus (Woodworth, 1900). Limnopus (Marsh, 1894), Dimetropus (Romer and Price, 1940), and Ichniotherium (Pohlig, 1892). These footprints can be referred to temnospondyl, basal synapsid (“pelycosaurian”), and diadectomorph trackmakers. The
moderately diverse tetrapod footprint assemblage from the Souss Basin is important because it is the second-oldest record of tetrapod footprints from Africa and only the second record of the wellknown ichnogenus Ichniotherium from outside of North America and Europe. Based on the variety of tetrapod tracks and previously collected floral and insect remains, the Souss Basin must have represented a well-established continental ecosystem during the Late Carboniferous.