Digital reconstruction of the Ceprano calvarium (Italy), and implications for its interpretation

Abstract

The Ceprano calvarium was discovered in fragments on March 1994 near the town of Ceprano in southern Latium (Italy), embedded in Middle Pleistocene layers. After reconstruction, its morphological features suggests that the specimen belongs to an archaic variant of H. heidelbergensis, representing a proxy for the last common ancestor of the diverging clades that respectively led to H. neanderthalensis and H. sapiens. Unfortunately, the calvarium was taphonomically damaged. The postero-lateral vault, in particular, appears deformed and this postmortem damage may have influenced previous interpretations. Specifically, there is a depression on the fragmented left parietal, while the right cranial wall is warped and angulated. This deformation affected the shape of the occipital squama, producing an inclination of the transverse occipital torus. In this paper, after X-ray microtomography (μCT) of both the calvarium and several additional fragments, we analyze consistency and pattern of the taphonomic deformation that affected the specimen, before the computer-assisted retrodeformation has been performed; this has also provided the opportunity to reappraise early attempts at restoration. As a result, we offer a revised interpretation for the Ceprano calvarium's original shape, now free from the previous uncertainties, along with insight for its complex depositional and taphonomic history.The hominid fossil calvarium discovered near Ceprano (Frosinone, Latium, Italy) represents a rather puzzling specimen in relation to other European hominins of the Middle Pleistocene 1 . For a decade after the discovery (March 13th, 1994), its chronology was considered to be around 800-900 ka 2-4 , whereas more recent data points to the beginning of MIS 11, providing a date bracketed between 430 and 385 ka 5 . This revised chronology corresponds to a time span when European cranial and postcranial samples already exhibited derived phenotypes shared with Homo neanderthalensis [6][7][8][9][10] . The absence of clear Neanderthal-like traits in the Ceprano calvarium 2-4 , combined with its unique combination of architectural and discrete features 4,11-13 , distinguishes the Italian specimen from great part of the penecontemporaneous fossil record in Europe, suggesting that its morphology probably persisted in an eco-geographic isolated refugium, while more derived morphs were spreading across the continent 1,14 .From a taxonomic point of view, since its discovery the Ceprano calvarium has been alternatively viewed as a "late" H. erectus 2 , a possible adult representative of H. antecessor 4 and even the holotype of a new species named H. cepranensis 15 . By contrast, Ceprano is more probably representative of an archaic variant of H. heidelbergensis 12 , furnishing evidence for the cranial morphology of the still poorly known stem subspecies (or paleodeme) of this taxon 1,16 .

Surface smoothing, decimation, and their effects on 3D biological specimens

“…Also, techniques such as photogrammetry and laser scanner, permit to virtually reconstruct biological objects or structures traditionally recorded by hand, for example burials or entire excavation sites (Ducke, Score, & Reeves, ; Grussenmeyer and Yasmine, ). CT‐scanning allows the study of internal structures of biological objects without any physical injury to the specimen, and it has provided excellent results in human evolutionary studies (Di Vincenzo et al, ; Mafart, Guipert, De Lumley, & Subsol, ; Spoor and Zonneveld, ; Tobias, ; Wind, ). Several other fields can benefit from the application of 3D digital methods.…”

A New Tool for Digital Alignment in Virtual Anthropology

“…Fossil remains often appear badly deformed by biostratinomic and taphonomic processes (Hughes and Jell, ; Arbour and Currie, ; Schlager et al, ) which usually result in major cracks, missing portions, or alteration of the biological symmetry (Ogihara et al, ; Arbour and Brown, ; Di Vincenzo et al, ). This lack of information can now be recovered by applying virtual reconstruction procedures, which take advantage of software implementations to perform the restoration of the digital versions of fossil remains.…”

“…DTA performs at least as well as manual alignments. Yet, as compared to manual procedures, it is faster, requires no prior anatomical knowledge and expertise and allows indefinite manipulation of the fossil items.Fossil remains often appear badly deformed by biostratinomic and taphonomic processes (Hughes and Jell, 1992;Arbour and Currie, 2012;Schlager et al, 2018) which usually result in major cracks, missing portions, or alteration of the biological symmetry (Ogihara et al, 2006;Arbour and Brown, 2013;Di Vincenzo et al, 2017). This lack of information can Additional Supporting Information may be found in the online version of this article.Abbreviations: AM = aligned model; DM = disarticulate model; DTA = Digital Alignment Tool; GPA = generalized Procrustes analysis; RM = reference model; SM = starting model…”

“…Fossil remains often appear badly deformed by biostratinomic and taphonomic processes (Hughes and Jell, 1992;Arbour and Currie, 2012;Schlager et al, 2018) which usually result in major cracks, missing portions, or alteration of the biological symmetry (Ogihara et al, 2006;Arbour and Brown, 2013;Di Vincenzo et al, 2017). This lack of information can Additional Supporting Information may be found in the online version of this article.…”

“…Missing morphological information can be digitally recovered either by using the preserved shape information on the deficient specimen (e.g., by exploiting biological symmetry) or through the use of a 3D comparative sample of phylogenetically close species, conspecifics, or individuals of the same sex (Gunz et al, 2009). Several case-studies are reported in the literature (Zollikofer et al, 2005;Benazzi et al, 2014;Amano et al, 2015;Di Vincenzo et al, 2017), and the use of virtual reconstructions is now becoming commonplace. Unfortunately, the efficiency of the virtual reconstruction is rarely quantified (e.g., Ogihara et al, 2006;Tallman et al, 2014;Schlager et al, 2018).…”