Vertebrate Ichnology

Objective: Provide a frame of reference for the recognition and interpretation of bezoars recovered from archeological and paleontological sites. Materials: 49 bezoars from extant guanaco (Lama guanicoe) were analyzed and compared with five objects previously identified as bezoars, recovered from Holocene archeological sites of the Argentine Pampas. Methods: Size, shape, weight, external and internal features, and mineralogical composition were evaluated in both modern and archeological bezoars using nondestructive and destructive methods. Results: Modern and archeological bezoars are formed by calcium phosphate and display great morphological variability linked to ante-mortem processes, taphonomic alterations, and anthropic activity. Conclusions: Morphometry, along with external and internal features and mineral composition, are useful tools for the identification and interpretation of bezoars in the fossil record. Significance: This study offers new information on the etiology, mechanisms of formation, and means of interpreting the presence of bezoars, a common pathology in South American camelids, in the fossil record. Limitations: The features of fossil bezoars do not provide accurate identification of the animal that produced them. Suggestions for Further Research: Further analyses on modern bezoars belonging to other species of mammals are needed in order to enhance the interpretation of bezoars in the fossil record.

At the Galinha tracksite (Serra d'Aire, West-Central Portugal) there are long sauropod trackways preserved on Middle Jurassic (Bajocian-Bathonian) limestones from the Lusitanian Basin. The paleoenvironmental study revealed that the sequence has been deposited in lacustrine, paralic and very shallow, restricted marine conditions. The Galinha site is a large and significant sauropod tracksite, is the oldest known in Portugal and represents one of the few Middle Jurassic dinosaur tracksites currently known. The site is characterized by having long and well preserved sauropod trackways (147 m and 142 m), and by some of the largest known trackmakers (pes length 95 cm, width 70 cm: manus length 40 cm, width 75 cm). There are complete and incomplete (consisting of manus-only impressions) trackways. They are wide-gauge and two of these trackways contain manus and pes sauropod prints having morphologies unknown in the worldwide track record. These appear to represent two new sauropod ichnotaxa. Opisthonyx portucalemis ichnogen. nov. and ichnosp. nov. is justified by two autapomorphies-manus prints with a large finger/claw I mark oriented in a posterior-medial direction and low heteropody (1/2). Polyonyx gomesi ichnogen. nov. and ichnosp. nov. is justified by two autapomorphies-asymmetric manus prints with a large triangular claw mark I oriented in a medial direction and pes prints with four claw marks: claws I-II oriented in an anterior direction; claws III-IV oriented laterally.

Body fossils of sea turtles are present in rocks dating back through the Cretaceous; traces of nesting activities of sea turtles ought to have a similar range. Recent loggerhead sea turtle nests have been extensively studied on St. Catherines Island, GA. Study and documentation of over 1450 nests and associated crawlways, and detailed trenching of more than 50 of these has led to a three dimensional model of modern sea turtle nests and the description of the sedimentary structures associated with nesting of the species Caretta caretta Linnaeus, 1758. The sedimentary structures studied present a recognizable spectrum of preservable traces dictated by a nesting ethogram consisting of nine described steps; 1) approach to the beach, 2) ascent of the beach, 3) wandering the beach, 4) wallowing to damp sand, 5) digging an egg chamber, 6) depositing eggs, 7) backfilling egg chamber, 8) covering activity, and 9) crawling to the sea. Loggerhead nest structures are elliptical with surface bioturbation masking underlying nest structures consisting of a body pit and egg chamber. Crawlways made during entering and leaving the nest, the thin veneer of bioturbated sand produced in the covering activity, and the underlying body pit and egg chamber are capable of preservation in ancient rocks. Successful incubation of sea turtle eggs could result in hatchling stopes, emergence craters, and fan-shaped patterns of hatchling crawlways; depredation of nests should result in recognizable sedimentary structures. The lack of recognition of ancient sea turtle nests may be partly due to the lack of description of Recent nests. The spectrum of potential nesting structures is obfuscated by the spatial constraints of differing viewpoints of biologists and geologists; the horizontal view of beach structures normally observed by biologists must be set in contrast to the vertical orientation of geologic information of geologists. This spectrum of potential sedimentary structures and disparate viewpoints has been partly validated, and is illustrated by the Cretaceous sea turtle nest described from the Fox Hills Formation of CO. The possible traces left by sea turtles are limited to nesting structures made by females nesting on sandy beaches in tropical or subtropical regions. Nesting behaviors are strongly imprinted on modern sea turtles and described as a nesting ethogram (Hailman and Elowson, 19xx) .The ethogram for loggerhead sea turtles (Caretta caretta) includes nine distinct segments each component of which results in characteristic traces of the behaviors that form potential trace fossils. The traces also provide a clue to the evolutionary sequencing of the behavioral segments; the presence of a covering activity (resulting in production of a covering pit) would imply depredation pressures existed in the past that led to the development of a hiding strategy. Although the beach has a low preservation potential, the abundance of nests year after year increases the potential for their preservation. The recognition of these structures in the fossil record is difficult due to their small size, cryptic appearance, and lack of experience of geologists with structures of this sort. The typical nesting ethogram would produce a suite of linked structures that can be depicted either verbally or diagrammatically: Loggerhead Ethogram Crawlways Crawlways are produced by the female sea turtle ascending and descending the beach and by hatchlings scampering to the ocean. The crawlway morphology (symmetry and nest morphology) allow the sea turtle conservationist to identify the species which produced the crawlway (Witherington, 19xx). Individual turtles produce identifiable crawlways due to attached epizoans, flipper pathology, and individual crawling characteristics. The direction the turtle was crawling may often be determined by asymmetrical push marks from rear flippers and by v-shaped drags made by claws on the front flippers that open in the direction of crawling. Because of this, entrance and exit crawlways can be identified and used in reading the nest. Once on the beach, the turtle may have to wander to find a suitable nesting site or might become disoriented and wander about after nesting trying to find her way back to the ocean; giving rise to a wandering pattern. Upon emergence, hatchlings produce radiating arcs of overlapping crawlways leading from their emergence crater to the ocean. Occasional misorientation, disorientation, or catastrophe can be read in their crawlway patterns. Body Pits Once the sea turtle senses a change in temperature from cool to warm as she passes from tidally-cooled to solar-heated sand at the high tide line, she will often attempt to nest. This is initiated by digging a body pit by wallowing and scraping dry surface sand away from and under her body ("wallowing down" to damp sand) so she can excavate an egg chamber in damp sand that will hold vertical wall due to its cohesion. Occasionally the turtle will encounter damp sand from at surface and produce a body pit in it right at the surface forming a distinctive nest morphology (a "sand angel" analogous to "snow angels" produced by children in fresh snow). Sand angels may also be produced by hatchlings if they hang up in vegetation or are flipped on their backs during their rush to the sea. Egg Chambers Once the sea turtle has wallowed down to damp sand, she will excavate an egg chamber using her rear flippers (try this yourself next time you visit the beach!) in an alternating scooping motion. The egg chamber is excavated to the depth to which the turtle can reach with her rear flippers and may show a bilateral symmetry in an urn-shaped excavation about 20-25 cm in diameter. Occasionally turtles will attempt nesting multiple times as they encounter subsurface obstructions (logs, wrack,, or roots) and may leave several open body pits and egg chambers behind as they scoot forward to try again. Once a suitable egg chamber is constructed the eggs will be extruded and the egg chamber backfilled, and possibly even tamped, with sand by the turtle's rear flippers. This filling is brecciated and in beaches with heavy minerals, will be obvious as a homogeneous, bioturbated sand cutting vertically through the horizontally laminated back beach facies. In horizontal view, if the loose sand of the covering pit is removed, this biogenic sedimentary structure will stand in stark contrast to the contour-like patterns of the back beach facies. The horizontal cross-sectional area of the egg chamber is usually less than 1% of the nest area; clearly an adaptation to protect eggs against depredation. Research Locations Recent loggerhead nesting structures have been studied on the beaches of St. Catherines Island, Georgia. Fossil structures were studied in the Fox Hills Formation of Elbert County, Colorado. St. Catherines Island is located midway on the Georgia Coast. Bishop and nested female loggerhead, McQueens Dunes, St. Catherines Island. Map view and cross-section of loggerhead sea turtle nest; St. Catherines Island, Georgia. Typical nesting structures of loggerhead sea turtle; North Beach, St. Catherines Island, Georgia. Scale = 10 cm. Loggerhead laying eggs in backbeach facies; US Fish & Wildlife Service. Eroded Recent sea turtle egg chamber in dune facies; South Beach, St. Catherines Island, Georgia. Scale = 10 cm. Egg chamber discontinuity in backbeach facies; South Beach, St. Catherines Island, Georgia. Scale = 10 cm. Egg chamber discontinuity in backbeach facies; South Beach, St. Catherines Island, Georgia. Scale = 10 cm. Loggerhead nest with covering pit, body pit, and egg chamber, trenched to investigate nest morphology and heavy mineral distribution; South Beach, St. Catherines Island, Georgia. Scale = 10 cm. Nested female loggerhead returning to sea after nesting and exit crawlway in backbeach facies (note v's opening in direction of crawl); North Beach, St. Catherines Island, Georgia. Scale = 10 cm. Hatchling loggerhead scrambling to sea after emergence and hatchling crawlways from emergence crater to sea in backbeach facies; North Beach, St. Catherines Island, Georgia. Scale = 10 cm. Paleogeography of Western Interior Seaway and approximate location of fossilized sea turtle nest structures in Elbert County, Colorado. Loggerhead nest on washover fan with adjacent body pit (bp) and covering pit (cp); North Beach, St. Catherines Island, Georgia. Scale = 10 cm. bp cp Documentation of loggerhead nest 95-104 on backbeach showing two unsuccessful body pits (bp) and the successful covering pit (cp); South Beach, St. Catherines Island, Georgia. Scale = ~ 1.0 m on smaller scale drawing.

In tetrapod ichnology, the morphologic quality of tracks is widely termed preservation, including both formational and postformational
processes; this study follows this interpretation. The term undertrack is generally referred to poorly-preserved
tracks found on the underlying layers of the actual trampled surface, which usually shows better-preserved tracks. This
study, using the most recent concepts and techniques in tetrapod ichnology, aims to give a significant contribution to the
understanding of the undertrack formation. The studied material includes some large temnospondyl tracks from the Early
Permian of the Lodève Basin (France), a trackway type material of Opisthopus and a pes-manus couple type material of
Laoporoides (nomen vanum), both assigned to Limnopus. These specimens show a peculiar feature: manual footprints that
are more distinct, more complete, deeper and classifiable (better-preserved) on the underlying layers (up to two underlying
layers) compared to the actual trampled surface, which shows shallower, indistinct and unclassifiable manual tracks (poorlypreserved).
Pedal tracks on the actual trampled surface are deformed and thus unclassifiable (poorly-preserved), and nearly
non-impressed in the underlying layers. This is probably the result of the trackmaker differential weight of manual and pedal
impressions on water-saturated fine-grained laminated sediments. This is the first convincing fossil evidence of a better
preservation of the undertracks in certain substrate conditions, confirming what is known from laboratory experiments. As
a consequence, caution is suggested in the interpretation of undertracks and surface tracks, and the term undertrack should
not be used as a synonym for poorly-preserved tetrapod tracks, although these terms often coincide.

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.

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