Lentiarenium cristolii Manja Voss & Björn Berning & Erich Reiter 2016, comb. nov.
Creators: name: Manja Voss
name: Björn Berning
name: Erich Reiter
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Sirenia
Dugongidae
Lentiarenium
Lentiarenium cristolii

description: Lentiarenium cristolii (Fitzinger, 1842) comb. nov.
Figs 2–10, Tables 1–5
Halitherium cristolii Fitzinger, 1842: 71, pl. 1.
Metaxytherium (?) pergense Toula, 1899: 459, pl. 12.
Halitherium abeli Spillmann, 1959: 36, pls. 1–4, fgs 19–20, 22, 24–27, 29b, 31–32, 33b, 34.
Manatus christolii – De Blainville 1844: 122.
Metaxytherium christolii – Laurillard 1846: 172.
Halianassa collinii – Meyer 1847: 189, 578 (partim). — Ehrlich 1850: 14–15, fgs a–c. — Ehrlich 1855: 3, pls. 1–2, corresponding fgs on pages 14–17.
Halitherium schinzii – Peters 1867: 310.
Halitherium schinzi – Lepsius 1882: 164 (partim).
Halitherium christoli – Abel 1904: 25, pl. 1, fgs 12–13, pl. 2, fgs 4, 11, 17, pl. 5, fg. 8, fg. 1. — Spillmann 1959: 17, fgs 8–18, 21, 23, 28, 29a, 30, 33a; 1969: 62, pl. 8, fg. 2; 1973: 198, pl. 40, fg. 4.
Halitherium pergense – Spillmann 1959: 11, fgs 6–7; 1969: 61, fg. 1; 1973: 197, pl. 39, fgs 1–2.
Halitherium abeli – Spillmann 1969: 62, pl. 9, fg. 3; 1973: 205.
Diagnosis
As for the genus.
Type Material
Lectotype (present designation)
A mandible (OLL 2012/1) of an adult individual (based on the presence of a large retromolar space and erupted m3 in wear) with left dp5–m2 and right m1–3, “Sicherbauer” sandpit, Linz.
Paralectotypes
Fragment of right maxilla with worn M1 crown and remnants of DP5 roots (OLL 2012/2), and an isolated crown of M3 (OLL 2012/3) from the right side, both from the “Sicherbauer” sandpit, Linz.
Holotype (by monotypy) of Metaxytherium pergense
Cast of a parietal-supraoccipital skullcap (OLL 1899/11), sandstone quarry near the town of Perg.
Holotype (by original designation) of Halitherium abeli
Mandible of an adult individual (based on the presence of a large retromolar space and erupted m3 in wear), fragments of basicranium, cervical and other vertebrae (OLL 1939/257), “Limoni” sandpit, Linz.
Referred material
OLL 1854/327, 1863/184, 1917/7, 1921/71, 1926/394, 1926/395, 1927/200, 1928/82, 1931/21, 1931/263,
1948/33, 2012/4, 2012/5, 2012/6, 2012/7, 2013/1. For a detailed listing of the preserved skeletal parts see Table 1.
Type horizon and locality
“Sicherbauer-Sandgstätte”, a former sandpit within the city limits of Linz (Upper Austria). Linz-Melk Formation, Linzer Sande (= Linz Sands), upper Oligocene, lower Egerian (Chattian).
Range and distribution
Known only from the upper Oligocene of Linz and the surrounding area.
Description
The following description is based on the available sirenian material housed in OLL, regardless of the different species that were proposed in the past. It will be outlined in detail in the Discussion why the respective skeletal material represents a single species.
Lentiarenium cristolii is known from cranial and postcranial elements. However, the premaxilla and lacrimal are unknown as are the pelvis, zeugopod and autopod. The following description is mainly based on a partial skull (OLL 1926/394) and two mandibles (OLL 1939/257 and OLL 2012/1).
PREMAXILLA. The premaxilla is not preserved in any specimen but some morphological characters can be indirectly determined. The external nares are retracted and enlarged (Fig. 2), as in all sirenians, and reach beyond the anterior margin of the orbit. Judging from the recesses in the anterior margin of the frontal, the nasal processes are not broadened and bulbous at their posterior ends but taper, having lengthy overlap with the frontals. The angle of the rostrum most likely exceeds 50° considering the defection of the mandibular symphysis of about 60° (Fig. 7).
NASAL. The exact status of the nasals cannot be determined without doubt due to the poor preservation of the nasal area in specimen OLL 1926/394 (Fig. 2). Judging from the right anteromedial margin of the frontals, which is not damaged, but smooth without an attachment area for the nasals, these elements are at least considered to have been small without meeting in the midline. A nasal incisure is present at
the posterior end of the mesorostral fossa, but unlike in Metaxytherium albifontanum (Velez-Juarbe & Domning, 2014a) and Priscosiren atlantica (Velez-Juarbe & Domning, 2014b) it is deep, extending posterior to the supraorbital processes of the frontals, though not to the extent seen in dugongines like Crenatosiren olseni (Domning 1997). It is uncertain whether the nasals were fused or coalesced with the frontals.
ETHMOIDAL REGION. The ethmoid is incompletely preserved and not easily observable in all aspects. A prominent perpendicular plate of the mesethmoid is visible in dorsal and anterior views of the skull OLL 1926/394 (Fig. 2). This vertical wall measures 10 mm to 15 mm in width, is narrower dorsally and ventrally, and apparently also becomes thinner posteriorly. Ventrally, the perpendicular plate is fused with the likewise distinctly developed vomer. On the right side of the skull, and medial to the frontal (Fig. 2), the almost complete large ethmoturbinal (concha maxima ethmoidalis (Kaiser 1974)) extends nearly parallel to the mesethmoid. Its left counterpart is only fragmentarily preserved. The crista galli and lamina papyracea are either not preserved or not visible.
VOMER. The vomer is exposed on the ventral side of the skull OLL 1926/394 but broken anteriorly (Fig. 3). It is fused with the presphenoid posteriorly and forms the cranial extension of its median crest. The vomer is triangular in cross section, frmly fused with the ethmoid via its fat dorsal surface, and contacts the maxilla laterally. In lateral view (Fig. 4B), the vomer is also visible through the orbit due to the incomplete preservation of the skull.
FRONTAL. In dorsal view (Fig. 2), the frontal roof is fat between the temporal crests, and bears no knoblike bosses as present in some dugongines (e.g., Crenatosiren olseni (Domning 1997)). The straight to slightly concave anterior margin of the frontal has no internasal process. The temporal crests form distinct keels (morphotype B; Domning 1988) and are as prominent on the frontal as on the parietal. In lateral view (Fig. 4B), the supraorbital process is dorsoventrally fattened with its dorsal surface inclined gently ventrolaterad. Its lateral margin is not divided, and it has a prominent posterolateral corner that projects posteriorly. An orbitotemporal crest is distinct relative to what is observed in Metaxytherium albifontanum (Velez-Juarbe & Domning 2014a), and forms a craniocaudally-extending ridge. The lamina orbitalis is signifcantly less than 10 mm thick.
PARIETAL. The parietal roof (Fig. 2) is fat between the temporal crests and characterised by a strong intertemporal constriction that reaches its maximum behind the centre of the skull roof with the parietal bulging laterally. An external sagittal crest is not developed. The frontal processes of the parietal are short and do not exceed half the length of the frontal in the midline, a condition similar to that in Priscosiren atlantica (Velez-Juarbe & Domning 2014b). The parietal is longer than the frontal, and the overall proportions of the cranial roof indicate a slight brachycephaly when the value of the frontal length is divided by the width of the supraoccipital, i.e., the ratio l FP/w SO, which is below 2. In endocranial view (Fig. 3), the bony falx cerebri extends from a prominent tentoric process and fattens out anteriorly before reaching the frontoparietal suture. The tentorium osseum is well developed and an internal parietal spine (or tentorial process as illustrated in Voss (2008: Fig. 4B)) is missing. On both sides of the bony falx, the fat internal parietal surface shows the depressions for the superior parts of the brain hemispheres.
SUPRAOCCIPITAL. This element is widest dorsally rather than ventrally (Fig. 4A), relative to what is observed in Metaxytherium spp. (e.g., M. albifontanum (Velez-Juarbe & Domning 2014a)). The supraoccipital is only slightly wider than high (width to height ratio <1.5), which is similar to the contemporaneous species Crenatosiren olseni (Domning 1997). Dorsally, the nuchal crest is constantly narrow along its transversal length and relatively sharp-edged. It makes up the dorsolateral margin of the supraoccipital. The external occipital protuberance rises above the parietal roof and is also prominent posteriorly. Ventrad, the protuberance continues as the external occipital crest that forms a distinct ridge, which slightly fattens out after one third of the supraoccipital’s height, almost reaching its ventral margin. Dorsolateral to this median ridge the deep and large insertions for the semispinalis capitis muscle occupy about the upper third of the external lamina. The area of the muscle insertion is triangular and defned by distinct ridges medioventrally and the nuchal crest dorsolaterally. The ventral margin of the supraoccipital forms an angle of approximately 135° in specimen OLL 1926/394. Specimen OLL 1899/11 (Fig. 5), formerly designated as the holotype of “ Halitherium ” pergense but now referred to Lentiarenium cristolii, also shows a distinct nuchal crest. However, the protuberance, median ridge and defnitions of the muscle insertions are less prominently developed than in OLL 1926/394, indicating its juvenile status. In interior view (Fig. 3), the supraoccipital is fat with the exception of longitudinal bulges dorsolaterally that are merged in the median plane and separated by a deep transverse sulcus from the tentorium osseum. Posterolaterally, the parietals extend between the supraoccipital and squamosal, forming a short fange.
EXOCCIPITAL. The dorsal parts of these paired elements are not preserved in any specimen. However, the total length of the ventral margin of the supraoccipital in OLL 1926/394 (Figs 3, 4A) reveals the articulation surface for the exoccipitals, indicating that these bones evidently meet in a suture dorsal to the foramen magnum. Additionally, specimen OLL 1939/257 preserves the ventralmost parts of the exoccipitals, which Spillmann (1959: fg. 19) illustrated in ventral view. During the personal examinations, the paroccipital processes were detected to be long, projecting as far ventrally as the occipital condyles, which is similar to what can be observed in some dugongines (e.g., Nanosiren garciae Domning & Aguilera, 2008 and N. sanchezi Domning & Aguilera, 2008 (Domning & Aguilera 2008: fg. 3, 11)). Medioventral to the paroccipital processes, the hypoglossal foramen is not opened to form a notch or incisure but is well surrounded by bone. The supracondylar fossae are distinct and defne the occipital condyles across their entire width.
BASIOCCIPITAL. An isolated basioccipital fused with the lower parts of the exoccipitals is preserved in specimen OLL 1939/257 (Spillmann 1959: fg. 19). It contributes to the occipital condyles ventrolaterally and extends craniad as a short, columnar bone. On its ventral side, the sphenooccipital eminences for the longus capitis muscles are concave and separated by a short but distinct ridge. Specimens OLL 1939/257 and 1926/394 (Fig. 3), in which either the basioccipital or basisphenoid is preserved, show smoothed attachment areas for the adjacent bone, indicating that the basioccipital and basisphenoid were not fused. On that basis, both specimens can be determined as subadults.
BASISPHENOID, PRESPHENOID, ORBITOSPHENOID. In specimen OLL 1926/394, the sphenoidal region is clearly observable (Fig. 3). The basisphenoid has a fat ventral surface that is defned laterally by antero posteriorly-broad pterygoid processes. Cranially, the basisphenoid continues with a slight anterodorsal slope into the presphenoid. Both bones are frmly fused with each other and with the orbitosphenoid anterolaterally, the alisphenoid dorsolaterally, and the pterygoid posterolaterally. The median crest of the presphenoid is not prominently developed, which might be related to the state of preservation of the skull in this area, and only becomes distinct at the level of the adjacent vomer. On the lateral side of the skull (Fig. 4B), the orbitosphenoid is exposed and contributes to the anteromedial wall of the temporal fossa. The orbitosphenoid is defned by the frontal dorsally, the alisphenoid posterodorsally, and apparently by the maxilla ventrally. Its sutures with the palatine are not detectable.
ALISPHENOID. The alisphenoid is visible in the lateral view of the skull (Fig. 4B). Its sutural contacts with the frontal, parietal and squamosal can be clearly determined. Furthermore, the alisphenoid forms the slightly uneven posterolateral side of the pterygoid process. An alisphenoid canal is absent, and the foramen ovale is opened to form a notch or incisure.
PTERYGOID. As in other sirenians, the pterygoid is present on the posteromedial side of the pterygoid process but fully fused with the surrounding bones (Fig. 3). Though not well preserved in OLL 1926/394, the wing-shaped pterygoid processes each bear a dorsoventrally elongated pterygoid fossa posteriorly that extends above the level of the roof of the internal nares, relative to the condition observed in some dugongines like Dioplotherium manigaulti (Domning 1989). The distal ends of both pterygoid processes are somewhat damaged, although the distomedial angle of the right pterygoid process is still distinct and indicates a hamula process.
PALATINE. Only the posteriormost parts of the palatines are preserved in OLL 1926/394, and are best observable on the right side (Fig. 3). There the palatine forms the anteromedial margin of the pterygoid process. Its sutures with the surrounding bones are only barely visible on the distal and medial sides of the pterygoid process and on the posterior side of the maxillary alveolar margin.
MAXILLA. The zygomatic-orbital bridge (Fig. 3) is not completely preserved in any of the specimens. However, in the maxillary fragment of OLL 1939/257 its dimensions are 47 mm in minimum length and 17.5 mm in nearly original height (Spillmann 1959: fg. 20). On the basis of these data, the zygomaticorbital bridge can be clearly determined to be long anteroposteriorly, relative to what is observed in the genus Hydrodamalis (Domning 1978; Velez-Juarbe & Domning 2014a). Additionally, and in contrast to some hydrodamalines, e.g., Dusisiren jordani Kellogg, 1925 and Hydrodamalis cuestae Domning, 1978 (Domning 1978; Velez-Juarbe & Domning 2014a), it is only slightly elevated above the alveolar margin, and its posterior edge is thickened. Remnants of the infraorbital canal reveal no obstruction.
SQUAMOSAL. The cranial part of the squamosal (Figs 2, 4B) extends up to the temporal crests but does not interrupt the course of the temporal crests, so that these reach the occipital nuchal crest. The posttympanic process is not club like distally (Fig. 4B), but concave anteroventrally for the attachment of the sternomastoid muscle. In the posterior view of the skull (Fig. 4A), a prominent sigmoid ridge is visible forming the laterocaudal margin of the squamosal. Posterolaterally, the mastoid foramen is present, flled by the periotic, and enclosed by the squamosal anteriorly, the exoccipital posteriorly, and the supraoccipital dorsally. Lateral to the braincase (Figs 2, 4B), each of the zygomatic processes projects from a zygomatic root that, though partially broken, is characterised by a distinct notch posteriorly. The zygomatic process is triangular in shape, tapering anteriorly. Its lateral and medial sides are fat to concave with the dorsal margin distinctly inclined inwards to form a sigmoid ridge. The posterodorsal end of the zygomatic process is straight to concave. The external auditory meatus is short mediolaterally and about as wide as high anteroposteriorly. Ventrally (Fig. 3), the elements of the mandibular articulation surface are elongated transversely. The mandibular fossa forms a distinct depression relative to the slightly convex tuberculum anteriorly. Posterior to the mandibular fossa, the postglenoid process forms a rounded and longitudinal knob, which rises above the level of the tuberculum. The posterior end of the zygomatic process, the processus retroversus, shows a moderate inward-directed infection in contrast to what is observed in the living dugong (e.g., Domning & Aguilera 2008; Velez-Juarbe & Domning 2014a).
JUGAL. Only a fragmentarily preserved middle part of the right jugal is known from specimen OLL 1926/394 (Fig. 4B), indicating that a postorbital process is probably present. Considering the position and shape of the supraorbital processes of the frontal, the development of a postorbital bar can be excluded. The zygomatic process of the jugal is not preserved but according to its imprint on the ventral side of the zygomatic process of the squamosal it reaches the tuberculum, exceeding the diameter of the orbit.
EAR REGION. In specimen OLL 1926/394, the right periotic is poorly preserved (Figs 3, 4A). It is not fused with the adjacent skull bones, and is set in a closely-ftting socket in the squamosal. The tegmen tympani is only indicated by its imprints on the dorsolateral side of the squamosal. It was most likely about as big as the mastoid or slightly smaller. The petrosal is fragmentarily preserved medioventrally, with the perilymphatic foramen apparently not separated into a fenestra rotunda and cochlea canaliculus. The processus fonticulus flls the mastoid foramen posteriorly (Fig. 4A).
MANDIBLE (Table 3). The mandibular symphysis is broad, as is the masticating surface that is lacking a median furrow and houses four large and shallow alveoli for vestigial incisors and canines. This is best visible in OLL 1939/257 (Fig. 6A), which exhibits a completely preserved masticating surface, whereas in OLL 2012/1 (Figs 6B, 7A) the ventralmost end is broken. In lateral view (Fig. 7), the symphysis is higher than long and bears the mental foramen laterally, which is joined dorsoposteriorly by two accessory mental foramina on each side in specimen OLL 1939/257 (Fig. 7B). The accessory mental foramina are large relative to what is observed in more plesiomorph dugongid taxa, e.g., “ Halitherium ” taulannense (Sagne 2001a), but they are still smaller than the principal foramen. This observation is interpreted here in analogy with Trichechus (Domning 1982, 1994, and personal observations), as “true” accessory mental foramina, which are present in addition to and usually posterior to the large principal foramen. In the lectotype (OLL 2012/1; Fig. 7A), the mental foramen is broken off dorsoposteriorly, and therefore the accessory mental foramina are not identifable, but their open canals are merged with the main foramen. The overall build of the horizontal mandibular ramus appears to be broad dorsoventrally, but it is evaluated to be slender on the basis of its minimum dorsoventral height, which is smaller than 0.25 × the length of the mandible. The ventral border of the mandible is strongly concave and not tangent to the angle posteriorly. The ascending mandibular ramus is incomplete, lacking most of the coronoid process, but still reveals a slight slope of it in the anterior direction. Posteriorly, the mandible is missing a distinct processus angularis superior and rather has a broadly convex outline. The mandibular condyle is well preserved in both specimens, with an articulation surface of even elliptical outline on a mediolateral axis. In OLL 1939/257 (Fig. 6A), the condyle is partially covered by plaster today but it is originally preserved as also stated by Spillmann (1959: 44, fg. 25). Behind m3 at the base of the ascending ramus (Fig. 6A), the coronoid foramen (canal) is enlarged and varies between 7.5 mm and 9.5 mm in maximum diameter. The retromolar space, i.e., the distance between m3 and the rear of the coronoid canal, is large in both specimens, measuring approximately 17 mm in OLL 2012/1 and 22 mm in OLL 1939/257. According to Domning (1978, 1988), it increases with age, indicating the adulthood of both specimens
(see also Sagne 2001b). In medial view (Fig. 6B), a single and undivided mandibular foramen reveals the dental capsule of m3 to be exposed posteroventrally.
DENTITION (Table 4). The premaxilla and anterior part of the maxilla are missing and therefore no conclusion on the absence or presence of incisor tusks can be drawn. However, the complete lower tooth arcade is preserved in two mandibles, one of which is the lectotype (OLL 2012/1). Accordingly, the dental formula in the lower jaw is interpreted to be i0, c0, p2–4, dp5, m1–3. Considering the logical occlusion pattern and the conditions in similarly derived sirenians, the second and third upper incisors are considered to be absent as are the upper canines while the permanent premolars P2–4 and the persistent DP5 are present. Consequently, the lifetime dental formula in the upper jaw is estimated to have been most likely?I1, C0, P2–4, DP5, M1–3.
Upper dentition. Besides the paralectotypes OLL 2012/2 and 2012/3, only two specimens have upper teeth or parts of these preserved. For example, OLL 1939/257 preserves a right maxillary fragment exhibiting the broken crowns and roots from M1–3 and DP5 (Spillmann 1959: fg. 20). The anterior part of the maxilla, especially the area where M1 and DP5 are positioned, is damaged and was restored. The medial and posterolateral roots of M1 are clearly preserved, whereas the anterolateral root is missing. The DP5 is three-rooted, as is characteristic for a molariform premolar that remains unreplaced. Its medial root is preserved but it is uncertain whether the anteriormost root in this maxillary fragment indeed belongs to DP5, representing one of the lateral roots, or may even be that of a single-rooted P4. In the frst case, the fragment including the anteriormost root was presumably fxed in the wrong position. The skull of specimen OLL 1926/394 preserves M1–3 from the right tooth arcade, the left M3, and the roots of the left M1–2, and therefore is the principal reference for the following description (Figs 3, 8).
The molars are three-rooted, not reduced in size relative to the skull and have well-developed enamel of about 2 mm thickness on average. Mesiobuccally, the right M1 is broken where the anterior cingulum might have been present, but it can be clearly identifed as the smallest molar. M1 is strongly worn in OLL 1926/394 as it is in the paralectotype OLL 2012/2, preventing any description of its cusp pattern except for the presence of two transverse lophs, an apparently deep central valley, and the postcingulum. The crown of M1 is heart-shaped in outline as is that of the slightly larger M2.
The right M2 (Fig. 8) is moderately worn and has distinct pre- and postcingula that attach to the two main transverse lophs mesio- and distolingually, and open labially by decreasing in height. The anterior and posterior basin each represent a deep furrow of similar size. Centrally, a deep transverse valley separates the protoloph from the metaloph but without being obstructed by the metaconule. The protoloph bears a continuous wear surface connecting the paracone labially, the protoconule centrally, and the protocone lingually, which are each still discernible as single cusps. The metaloph is slightly less worn and reveals the nearly transverse row consisting of metacone and hypocone from labial (or buccal) to lingual, with the metaconule in between only very slightly shifted anteriorad. Despite tooth wear, these posterior cusps can still be clearly distinguished from each other.
The right upper M3 is well preserved in specimen OLL 1926/394 and only slightly worn (Fig. 8). This stands in contrast to the state of preservation of the paralectotype OLL 2012/3, an isolated right M3 that shows a strongly worn protoloph and is broken distolingually. However, both teeth resemble each other in shape and are also similar in their preserved morphology. The M3 is larger than M2 with its crown in the shape of an elongated heart due to the distal metaloph being transversally shorter than the mesial protoloph. Proto- and metaloph are each characteristically composed of three cusps. Accessory cusps or cuspules are not present. The main cusps of the protoloph form a transverse row, and are clearly separated and distinct from each other. Lingually, the protocone represents the largest and highest cusp followed in the buccal direction by the smaller protoconule and paracone, both of about the same size. A cuspid precingulum is attached mesiolingually to the protocone and opens labially by decreasing in height. The anterior basin forms a deep furrow. Proto- and metaloph are separated by a distinct transverse valley that is somewhat obstructed but not closed by the slightly anterad-shifted metaconule. The hypocone is slightly larger than the subequally-sized metaconule and metacone, and closely adjacent to the metaconule but still separated from it by a distinct furrow. The posterior basin is large and deep, and enclosed by two cingular cusps that form the postcingulum, which is connected to the hypocone lingually and opens labially.
Lower dentition. Two individuals of approximately the same age or state of tooth wear preserve the lower dentition. Mandible OLL 1939/257 preserves both tooth arcades (Fig. 6A), and the lectotype specimen OLL 2012/1 has only the right arcade complete while the left one is broken behind m2 (Figs 6B, 7A). The masticating surface of the mandibular symphysis (Fig. 6A) bears four large and irregularlyrounded alveoli that are not very deep, and may have housed three pairs of vestigial incisors and one pair of vestigial canines. These alveoli gradually diminish in size top down, with the topmost alveolus measuring approximately 20 mm × 15 mm in diameter and the lowermost alveolus measuring 15 mm × 10 mm in diameter. The teeth themselves are not known, nor are the permanent premolars p2–4.
A further alveolus is present at the junction between the masticating surfaces of the horizontal mandibular ramus and the mandibular symphysis. It resembles in size and outline the alveoli of the vestigial lower incisors and canines, and is interpreted here to have possibly housed a vestigial dp1, which is not replaced at this locus. The paired roots of dp5 are preserved in both mandibles, but in specimen OLL 1939/257 (Fig. 6A), though heavily worn, the left crown is present, indicating a molariform tooth. Its protolophid and hypolophid have about the same transversal length.
Molars m1–3 are preserved in both specimens and characterised by having two roots and mesiodistallyelongated crowns that slightly increase in size from anterior to posterior within the tooth arcade (Fig. 6A). All crowns are moderately to heavily worn, preventing most details of their cusp pattern from being observed except for the two main transverse lophs, which are separated by a deep transverse valley. The protolophid and hypolophid are nearly perpendicular to the longitudinal axis of the tooth arcade. In the lectotype specimen, m2 and m3 are slightly less worn than in specimen OLL 1939/257 and reveal the transverse valley to be obstructed by an accessory cuspule that is connected to the hypoconid mesiointernally. This might have also been the case on m1, which, however, is too heavily worn to draw unambiguous conclusions. While the protolophid is about as large transversally as the hypolophid on m1, the hypolophid decreases in size from m2 onwards and becomes distinctly shorter on m3. Additionally, the bicuspid morphology of the protolophid and hypolophid is still discernible on m3. This becomes more obvious in a nearly unworn isolated m3 (OLL 2012/6) from the left side (Abel 1904: pl. 1: fg. 13). There the metaconid forms a prominent lingual cusp that is slightly larger than the protoconid on the labial side. On the hypolophid, the entoconid is about as large as the hypoconid. Also the isolated m3 (OLL 2012/6) displays a mesiointernal accessory cuspule of the hypoconid. A precingulum is not detectable on any molar. The hypoconulid lophule is distally composed of two cusps in OLL 2012/1 that are vaguely observable also in OLL 1939/257 (Fig. 6A). Specimen OLL 2012/6 shows two additional cuspules between the two cusps that might no longer be observable in the former two specimens due to wear.
HYOID APPARATUS. Not preserved in any specimen.
VERTEBRAL COLUMN. The vertebral column is only incompletely known by a few cervicals, several thoracics, some lumbars, and caudals. Most of the vertebral remains are associated with two partial skeletons, OLL 1854/327 and 2013/1. The ribs and vertebrae of specimen OLL 2013/1 are lost today and only documented in Spillmann (1959: fg. 2). Otherwise, the vertebrae are only known by fragments as also indicated by Spillmann (1959), but these also seem to no longer be available in the collections of the OLL. Relative correlation to a position within the column is partly possible.
Cervicals. The atlas is almost completely preserved in specimen OLL 1939/257. Both cranial articular facets are well defned and form concave and kidney-shaped areas for articulation with the occipital condyles. The caudal articular facets are slightly fatter and have a rounded outline without the large dorsoventral extension as in their cranial counterparts. The lateral margins of the articular facets fare out so that the articular surfaces are somewhat directed medially, toward the vertebral canal. The vertebral foramen is large, occupying the centre of the atlas, and partially obstructed at about half its height by a small bony knob on the right side for the transverse ligament. This knob certainly was present also on the left side but it is no longer preserved, and this area is replaced by plaster now. The neural arch is a low ridge with a small triangular surface anterodorsally that possesses a narrow and low median keel about 10 mm long. The anterior surface rises slightly in the dorsocaudal direction, whereas dorsocaudally the neural arch is not inclined but forms a smooth and rounded ridge.
Laterally, the atlas shows caudad-projecting aliform transverse processes, the left one broken to its base. Ventral and medial to the transverse processes the foramen transversarium is located, measuring about 2 mm in diameter. The vertebral foramen is defned ventrally by a bony bridge about 10 mm long anteroposteriorly and missing the caudad-projecting articulation surface for the second cervical, the area of which is replaced by plaster now.
Specimens OLL 1939/257 and OLL 1854/327 preserve a further vertebra from the cervical series, the latter only observable in caudal view, due to its arrangement on the in situ reconstruction, and missing the transverse and caudal articular processes. Both vertebrae represent elements of the series C3–7, but their exact position within the cervical column cannot be determined. The centra are short anteroventrally and form the fat foor of the vertebral foramen that is overall rounded although slightly peaked dorsally. Dorsal to the centra the neural arch is preserved, with a short neural spine rising straight up and having a slight keel cranially and a somewhat concave surface caudally.
Thoracics. Both partial skeletons, OLL 1854/327 and 2013/1, as well as specimen OLL 1939/257 preserve thoracic vertebrae. Their morphology does not importantly differ from that of other Oligocene sirenians like P. atlantica (Velez-Juarbe & Domning 2014a) and those formerly lumped under “ Halitherium schinzii ” and now in the process of being published (Voss & Hampe accepted). The description is therefore generalised in the following.
Specimen OLL 1939/257 preserves the frst thoracic, T1, which is similar to the T1 remains illustrated for M. albifontanum (Velez-Juarbe & Domning 2014a: fg. 10C). The cranial and caudal epiphyses are more or less equal in size, but fat to concave cranially and slightly convex caudally. Lateral to the centrum, wing-shaped transverse processes are present, the right one broken to its base. The left transverse process extends laterad with a slight slope in caudal and ventral directions. The rear side of the process is fat to slightly concave. In cranial view, the prezygapophyses are fat dorsally and directed anterolaterad. In caudal view, the right postzygapophysis is present dorsal to the transverse process at a somewhat higher level than the prezygapophyses. Although the posterior tip is broken, it can be clearly determined that the articular facet for the adjacent cervical is directed ventrad and posteromediad. The neural spine rises straight up from the neural arch and is broken at about half of its height, but clearly shows a slight keel cranially and a somewhat concave surface caudally.
The centra of the remaining thoracics are compact elements with a roughly heart-shaped outline that is caused by a more or less pronounced ventral crest and a shallow longitudinal depression dorsally. Dorsolaterally, the centra show deeply concave cranial and caudal articular facets for the capitula of the corresponding ribs while the remaining lateral surface is fat to slightly concave. The cranial and caudal extremities are fat and always wider than high. Lateral to the base of the neural arch, the transverse processes originate as very short and wedge-shaped elements with a slight dorsad slope. In ventral view, the transverse process bears the rounded articular facet for the tuberculum of the corresponding ribs. The mammillary processes form prominent knobs on the cranial sides of the transverse processes. Dorsal to the rounded and keyhole-shaped vertebral foramen, the cranial and caudal zygapophyses are present with the former fattened dorsally and the latter fattened ventrally. In anteroposterior direction, the neural spines are about as long as the centra and rise straight up with their cranial surface keeled and the caudal surface cleaved. Some thoracics are preserved in a somewhat oblique position in OLL 1854/327 and reveal a tuberosity on the distal end of the neural spine that seems to extend longitudinally in the anteroposterior direction. Vascular canals can be variably present on the vertebrae, especially on the ventrolateral and dorsal surfaces of the centra.
Lumbars. Specimen OLL 1854/327 preserves a single lumbar composed of the centrum and the transverse processes. This vertebra is only observable in cranial view due to its arrangement on the in situ reconstruction. The vertebral body is massive with an oval outline that is wider than high. Its lateral and ventral surfaces are fat and the cranial epiphysis is slightly concave. The neural arch is not preserved. Though partially broken on the left side, the transverse processes are long mediolaterally, and attach with craniocaudally-broad bases lateral to the mid-section of the centrum. In cranial view, they extend more or less horizontally and show only a slight ventrocaudad inclination. The dorsal and ventral surfaces of the transverse processes are smooth and terminate in narrow and blunt distal ends. Therefore, this vertebra is not considered to represent a sacral vertebra as it evidently did not serve for the attachment of the pelvic ligaments, but has to be assigned to the lumbar series. Its exact position within the lumbar segment remains uncertain.
Caudals. Some caudal vertebrae were present in the partial skeleton OLL 2013/1, which is the only reliable information up to now. As mentioned above, however, this specimen is no longer available or at least not recognisable in the OLL collections. Additionally, the caudals are simply recorded in Spillmann (1959) but neither described in detail nor illustrated except for the schematic documentation of the original fnd context, which, however, barely deals with these elements.
CHEVRONS. Not known in any specimen assignable to Lentiarenium cristolii.
RIBS. Abundant rib fragments are known while the two partial skeletons OLL 1854/327 and 2013/1 (now lost) provide several complete ribs. Most elements are known from specimen OLL 1854/327, which preserves 34 ribs and rib fragments. However, no example of the frst rib exists. No measurements could be taken from the preserved ribs in specimen OLL 1854/327, because the bones are mounted in their original position. Nonetheless, the ribs are identifed as long, slightly arching elements, having an overall morphology that does not differ from other Oligocene sirenians like those formerly lumped under “ Halitherium schinzii ” (Voss & Hampe accepted). The ribs are pachyosteosclerotic, mediolaterally fattened, and hence have an elliptical cross section similar to what is observed in P. atlantica and M. albifontanum (Velez-Juarbe & Domning 2014a, b).
STERNUM. Two sternal fragments are preserved, OLL 2012/5 (Fig. 9C; Abel 1904: fg. 1; Spillmann 1959: fg. 33a) and 1948/33. Specimen OLL 1948/33 (Spillmann 1959: fg. 33b) was found in 1944, as was the partial skeleton OLL 2013/1. However, it is not certain if both belong to a single individual, and this uncertainty is also indicated by a separate collection number for the sternal part. Therefore, OLL 2013/1 and 1948/33 are treated here as two different specimens.
Specimen OLL 2012/5 measures 84 mm in maximum length and 65 mm in maximum width, and is the smaller of the two sternal fragments as well as the better-preserved one (Fig. 9C). Abel (1904: 36) identifes that element as the “processus ensiformis” of the xiphisternum. Spillmann (1959) considered it to be part of the corpus. In this study, Abel’s (1904) interpretation is confrmed, and this element is considered to represent the anterior part of the xiphisternum. The bone has smooth dorsal and ventral surfaces, the former slightly convex and the latter slightly concave. In the caudal direction the bone slightly widens, while a blunt process is present anteriorly. The lateral margins are thickened anteriorly, each characterised by two articulation facets for the attachment of ribs. The lateral margins become thinner caudally forming sharp edges. OLL 1948/33 most likely represents a fragment of the manubrium, which preserves a single rib articulation facet on each side. The bone has smooth surfaces and lacks a ventral keel.
SCAPULA (Table 5). Three scapular remains were described by Spillmann (1959), one of which represents the distal two-thirds of the left element (OLL 1854/327; Fig. 10). Additionally, the partial skeleton OLL 2013/1 preserves parts of the left scapular blade. The right element of this specimen was originally also present (Spillmann 1959) but is now lost.
The scapular blade is sickle-shaped, defned by the margo cranialis anteriorly, the margo dorsalis proximally, and the margo caudalis posteriorly. The anterior margin steeply rises craniodorsad with an angle of about 50° from the collum scapulae, i.e., the scapular neck, and turns at nearly a right angle to run more or less straight dorsad for about 100 mm. Specimen OLL 1854/327 is broken at this level (Fig. 10; Spillmann 1959: fg. 30), but the left scapula of OLL 2013/1 (Spillmann 1959: fg. 31) preserves the proximal end that shows a dorsocaudal slope of about 45° into the margo dorsalis. The latter extends approximately 100 mm almost parallel to the vertebral column and, fnally, forms an angle of about 90° with the margo caudalis. It is only this short margo dorsalis that is broadened and roughened for attachment of a scapular cartilage, in contrast to the thin and sharp anterior edge immediately distal to it. The posterior margin is largely convex cranially, and converges distad together with the margo cranialis to form the long and slender collum of about 50 mm in dorsoventral length, which is best visible in OLL 1854/327 (Fig. 10).
The external surface (Fig. 10A) is divided by the scapular spine into a large and shallow supraspinous fossa, and a narrow and more concave infraspinous fossa. The scapular spine forms a rounded fange without a proximal rugosity and does not exceed half the length of the scapular blade. It starts with a broad base at about the middle portion of the blade and rises slightly but steadily towards its distal end.
The spine becomes narrower in the distal direction by sloping slightly caudad and, fnally, terminates in the acromion. Although the acromion is broken in all specimens, it can be clearly stated that it did not pass the level of the glenoid cavity. Similar to what is observed in M. albifontanum (Velez- Juarbe & Domning 2014a), the coracoid process is moderately developed, inclined medially, and is not disjunct from the anterior apex of the articular glenoid (Fig. 10B). The glenoid cavity is shallow and oval, narrower mediolaterally and wider anteroposteriorly, about 25 mm × 48 mm in OLL 1854/327. Medially (Fig. 10B), the costal surface is overall fat and smooth, only slightly convex in its central part according to the curvature of the ribs.
HUMERUS. Two single fragments of the left humerus from different individuals are known. Specimen OLL 2012/4 represents a left proximal half of 115 mm length in its maximum dimensions (Fig. 9A–B), and specimen OLL 2013/1 preserves a distal fragment that was excavated together with the partial skeleton in 1944. Although incompletely preserved, the humerus is seen to be compact and having distinctly developed epiphyses. The diaphysis forms a strong shaft but it is broken in both specimens and preserves only remnants of the deltoid crest anteriorly in OLL 2012/4 (Fig. 9B). The humeral head is rounded and separated by a deep furrow from the lesser tubercle. Both the lesser and greater tubercles are broken. The bicipital groove is deep and wide, serving for the passage of the biceps muscle. On the distal fragment (Spillmann 1959: fg. 32), the lateral and medial epicondyles are barely preserved. However, the trochlea can be identifed as an hourglass-shaped and smooth articulation surface for the radius and ulna. Its inclination relative to the shaft appears to be perpendicular but cannot be certainly determined due to the incomplete state of preservation.
Remarks
Lentiarenium cristolii was originally based on a type series according to Fitzinger (1842). This type series was composed of a mandible with left dp5–m2 and right m1–3 (OLL 2012/1), two isolated molars (OLL 2012/2 + 3), an isolated m3, ribs and vertebrae. In the above order, all syntypes were found in the “Sicherbauer” sand quarry in 1839 (Spillmann 1959: 4), but in succession and not at the same time as indicated by Fitzinger (1842: 62). Hence, it is not certain whether the original type series represents a single specimen. In the interest of nomenclatural stability, the mandible is designated here as lectotype. Accordingly, the remaining syntypes in the type series of Fitzinger (1842) represent paralectotypes. The ribs and vertebrae mentioned by Fitzinger (1842) are no longer traceable in the OLL. According to Fitzinger (1842), an isolated m3 was sent to the Naturhistorisches Museum Wien, Austria (NHMW) but it is neither listed in the catalogue of Pia & Sickenberg (1934) nor present in the NHMW vertebrate collection itself (pers. comm. U. Göhlich). These elements are now considered to be lost.
Furthermore, it is proposed in this study to maintain the original spelling of the species name cristolii as established by Fitzinger (1842), and to regard the use of “christoli” and “ christolii ” as incorrect subsequent spellings. Although Fitzinger (1842) established this species in honour of Jules de Christol, he spelled the name “de Cristol” (p. 67) and consistently applied the spelling “ cristolii ” throughout his entire work, which shows that it is not a lapsus calami or printer’s error. Therefore, “ cristolii ” (Fitzinger 1842: 71) is the “correct original spelling” according to Articles 32.1., 32.2. and 33.4. of the Code (ICZN 1999), and is not to be considered as a spelling that must be corrected following Article 32.5.1.
As already stated by Marx et al. (2010) and Berning (2013), the OLL collection numbers are another source of confusion. Some of the fossil fnds of the 19th and early 20th century were apparently not given a collection number when they came to the museum. At some stage between 1914 and 1937 the fossil vertebrates were transferred from the palaeontological collection to the biological collections, which were then curated by the vertebrate specialist Theodor Kerschner. It was he who gave consecutive numbers to the fossil vertebrate remains using his own system, ignoring that some of the specimens already had offcial collection numbers. Kerschner’s unoffcial numbers, however, which start with an abbreviation of the respective taxon (e.g., “Sir.1”= Sirenia #1), were often used in publications during the 20th century (e.g., Spillmann 1959). For the sake of conformity with the numbers of the larger part of the palaeontological collection, we return here to using the offcial collection numbers (see Table 1 for comparison between Kerschner’s and the offcial numbers). Specimens without such an offcial collection number, i.e., those we could not trace in the collection register, were given new numbers.
description: Published as part of Manja Voss, Björn Berning & Erich Reiter, 2016, A taxonomic and morphological re-evaluation of " Halitherium " cristolii Fitzinger, 1842 (Mammalia, Sirenia) from the late Oligocene of Austria, with the description of a new genus, pp. 1-32 in European Journal of Taxonomy 256 on pages 7-24, DOI: 10.5852/ejt.2016.256, http://zenodo.org/record/889326