Lentiarenium

Lentiarenium
	Lentiarenium cristolii ; Lower jaw OLL 2012/1 (A) and OLL 1939/257 (B)
Temporal occurrence
	Upper Oligocene
	25.8 to 23.03 million years
Locations
	Upper Austria ( Linz , Perg ); Lower Austria ( Wallsee );
Systematics
	Mammals (mammalia)
	Afrotheria
	Tethytheria
	Manatees (Sirenia)
	Fork tailed manatees (Dugongidae)
	Lentiarenium
Scientific name
	Lentiarenium
	Voss , 2016
Art
	Lentiarenium cristolii ( Fitzinger , 1842);

Lentiarenium is an extinct genus of the fork tailed manatees (Dugongidae). The only known species of the so far monotypical genus is Lentiarenium cristolii from the Upper Oligocene ( Chattium ) in the vicinity of Linz ( Upper Austria ) and neighboring areas in Lower Austria .

Research history and etymology

In April 1839 the heavily fragmented lower jaw as well as several ribs and vertebral bones of an initially unknown animal were found in the so-called "Safe Builders Sandgstätten", a former sand pit in what is now the city of Linz, and handed over to the "Museum Francisco-Carolinum" . A short time later, further specimens followed (two isolated molars ) and finally in October 1840 a third molar from the same site, which was handed over to the “Imperial Museum of Natural History” in Vienna.

Georg Weishäupl , at that time curator at the “Museum Francisco-Carolinum”, and the museum attendant Voigt succeeded in reassembling the individual fragments of the lower jaw into a nearly whole. Weishäupl made a drawing of the fossil and sent it along with a report to Paul Partsch , the curator of the mineralogical department of the kk Hof-Naturalien-Cabinet in Vienna. Partsch left the documents to Leopold Fitzinger , who was able to correctly identify the fossil as the lower jaw of an extinct species of manatee . The fossil is now under the inventory number OLL 2012/1 at the Upper Austrian State Museum (OLL).

Leopold Fitzinger

Fitzinger placed the new species in the genus Halitherium described in 1838 by Johann Jakob Kaup from the Tertiary of the Mainz Basin . The genus Metaxytherium described by Jules de Christol in 1840 was assessed by Fitzinger as being identical to Halitherium and he accordingly preferred the, from his point of view, older name. In consideration of de Christol's merits, however, Fitzinger chose the term cristolii as a species addition . Fitzinger used the spelling “de Cristol” or “ cristolii ” throughout his first description . Although both orthographically and grammatically deficient, the designation “ cristolii ” is valid according to the rules of the ICZN code and later spellings such as “ christolii ” or “ christoli ” should be discarded.

Hermann von Meyer put the finds from the "Safe Builders Sandgstätten" in 1843 in the genus Halianassa, which he also established in 1838, and named it four years later as Halianassa collinii .

In August 1854 the partial skeleton (OLL 1854/327) of a fossil manatee was found in the so-called "Prixenhäusl sand pit" in Linz. Franz Carl Ehrlich described the find in 1855 together with a left shoulder blade from the same site and two skull fragments. Ehrlich followed Meyer's name in his description and referred to both the finds from the "Sicherheitsbauer-Sandgstätten" and those from the "Prixenhäusl-Sandgrube" as Halianassa collinii .

Franz Toula

In 1899 Franz Toula described the roof of the skull and the corresponding stone core of the skull of a manatee from sediments of the same age from Perg in Upper Austria. Toula was unsure about the genus belonging to the fossil remains of Perg and referred to them as a possibly new representative of the genus Metaxytherium as Metaxytherium (?) Pergense . In 1904, Othenio Abel contradicted this assessment in a more detailed treatise on "The Sirens of the Mediterranean Tertiary Educations in Austria". He synonymized Metaxytherium (?) Pergense with the finds from Linz, using the name Halitherium christoli , based on the original naming by Fitzinger . Abel interpreted the anatomical differences ascertained by Toula as lying within the range of variation of a natural species or as an expression of different ontogenetic stages.

The next more comprehensive analysis of the Oligocene manatees in Austria was more than half a century in coming. In 1959 Franz Spillmann published his treatise on "The Sirens from the Oligocene of the Linz Basin (Upper Austria)". The scope of the available evidence had meanwhile increased considerably. Vertebral and rib fragments were among the more common finds from the sand pits of Linz, Perg and St. Georgen an der Gusen in Upper Austria and Wallsee in Lower Austria. Numerous finds came primarily from the sand pits on the western edge of the Linz basin , in the area between Römerberg , Freinberg and Froschberg , so that Spillmann referred to the area in 1959 as the "Siren Bay".

Other postcranial skeletal elements or even parts of the skull, on the other hand, were rarities; but all the more important for a diagnosis . Of particular importance were the discovery of a skull (OLL 1926/394), which was recovered from the so-called “Jungbauer sand pit” in Linz in 1926 and which Spillmann assigned to the taxon Halitherium christoli in 1959 , as well as another, almost complete lower jaw (OLL 1939/257) which was found in 1938 together with parts of the base of the skull, a fragment of the upper jaw and parts of the cervical spine in the "Limonikeller" in Linz. Spillmann described the latter find in 1959 together with postcranial skeletal elements from St. Georgen an der Gusen as the new species Halitherium abeli . At the same time he reactivated the Perg finds described by Toula again as an independent species Halitherium pergense .

In 1994 the pendulum swung again in the opposite direction between lumper and splitter and Daryl P. Domning evaluated Halitherium pergense and Halitherium abeli in a more comprehensive phylogenetic analysis as identical to the species already described by Fitzinger, using the spelling Halitherium christolii . Domning failed to provide appropriate arguments to support his assessment. After Manja Voss had already pointed out in 2014 that there was no valid definition for the type species of the genus Halitherium ( Halitherium schinzii Kaup , 1838) and thus also for the genus itself, she examined the findings together with Björn Berning and Erich Reiter the Oligocene of the Linz Basin a new analysis. The authors found no evidence that the Upper Oligocene coasts of the Linz Basin were inhabited by more than one species of manatee. As part of the revision of the discarded genus Halitherium , the species Halitherium christolii , Halitherium pergense and Halitherium abeli propagated by Spillmann were combined and placed as Lentiarenium cristolii in the new genus Lentiarenium .

The new generic name Lentiarenium is made up of " Lentia ", the name of the Roman fort and the associated civil settlement in what is now the city of Linz, and " arenium " from the Latin " arena " ("sand"). The term refers to the “Linzer Sande”, the informal name for the Upper Oligocene sands of the Linz-Melk Formation from which the finds originate.

Synonyms of the type species

The rather turbulent history of research is reflected in a large number of synonyms for the type species of the genus Lentiarenium :

Halitherium cristolii Fitzinger , 1842
Halianassa collinii Meyer , 1847
Metaxytherium (?) Pergense Toula , 1899
Halitherium christoli Fitzinger , 1842
Halitherium pergense ( Toula , 1899)
Halitherium abeli Spillmann , 1959
Halitherium christolii Fitzinger , 1842
Lentiarenium cristolii ( Fitzinger , 1842)

Age assignment of the finds

The sands of the Linz-Melk Formation in the urban area of Linz can be assigned to the lower egerium of the regional chronostratigraphic structure of the central Paratethys on the basis of biostratigraphically usable foraminifera , mollusks and the remains of terrestrial vertebrates washed into the deposit area , which is the upper chattium of the international chronostratigraphic structure corresponds. The deposits further to the east, some of which have already solidified to form sandstone, are regarded as a stratigraphic equivalent. However, many details of the stratigraphy of the Linz-Melk Formation are still unclear and Voss et al. indicate in 2016 the chronostratigraphic distribution of Lentiarenium with Upper Oligocene (Chattian) and Lower Egerian, which corresponds to an absolute age of 25.8–23.03 Ma .

features

Skull (OLL 1926/394) in a dorsal view

Skull (OLL 1926/394) in an anterior view

Skull (OLL 1926/394) in caudal (A) and lateral (B) view

Unless otherwise stated, the description of the characteristics essentially follows the diagnosis by Voss et al., 2016. Abbreviations in brackets refer to the corresponding figures.

The skull of Lentiarenium cristolii shows typical features of a representative of the fork-tailed manatees (Dugongidae). A canalis alisphenoidalis (= canalis alaris), an opening in the wing process of the sphenoid bone ("as") through which the maxillary artery runs, is missing, as in all more highly developed sirenia . This feature is only preserved in the most primitive representatives of the Sirenia, such as Prorastomus , Pezosiren or Protosiren . The foramen ovale is open and forms an indentation. The fifth premolar (“dp5”) is not replaced and the scaly bones (“sq”) extend to the strongly developed temporal edges (= Linea temporalis sensu Spillmann, 1959; = “temporal crests”; “tcr”), the attachment points of the temporal muscle in the area of the parietal bone ("p").

Lentiarenium different from the Dugonginae ( Bharatisiren , Callistosiren , Corystosiren , Crenatosiren , Dioplotherium , Domningia , Dugong , Kutchisiren , Nano Irish , Rytiodus and Xenos Irish ), the Hydro Dama Linae ( Dusisiren and Hydrodamalis ), and other representatives of Dugongidae ( Caribosiren , Eosiren , Eotheroides , Metaxytherium , Priscosiren , Prototherium and other forms that were originally summarized in the genus Halitherium , such as Kaupitherium , formerly Halitherium schinzii ) through the following combination of characteristics:

The frontal bone ("f") is flat between the temporal edges ("tpc") and has no knot-like humps , as can be seen in crenatos . The processus supraorbitalis ("sop"), an extension of the frontal bone, is flattened dorsoventrally and shows a clearly pronounced, approximately triangular, laterally rearwardly directed process. The supraoccipital (“so”) is wider dorsally than ventrally . The exoccipital, paired bones of the base of the skull, are only partially preserved in the fossil record available to date. The corresponding attachment points on the supraoccipital, however, indicate that the two bones met in a common suture dorsal to the foramen magnum . The processus posttympanicus ( "ptymp"), a bone extension below the external auditory canal ( "EAM") shows anteroventral a significant extension as a starting point for the musculus sternomastoideus, a connection between the skull and sternum is prepared. The paroccipital process, an extension of the exoccipital that serves as a muscle attachment, is long and extends ventrally to the occipital condyle .

On the lower jaw , the mental foramen (“mef”) is accompanied by other, similar but smaller openings (“accessory mental foramina”, “accessory mental foramen”, “amef”). The horizontal part of the lower jaw branches ("hmr") is slender dorsoventral.

Dentition

Lower jaw OLL 1939/257 in occlusal view

The symphysis area (“msym”) of the lower jaw is strongly bent downwards and the chewing surface (“mas”) in this area forms an angle of about 120 ° with the chewing surface in the area of the molars . With the recent dugong ( Dugong dugon ) the value is around 110 °. The chewing surface in the symphysis area is covered with a horn plate in the recent Dugong . Underneath, there are four stunted teeth, three incisors and the canine on each half of the lower jaw , but these do not completely break out of the jawbone. The well-known remains of the lower jaw from Lentiarenium also show four alveoli per half of the jaw in this area . However, the associated teeth are not preserved in fossil form. Another alveolus is located in the transition between the symphysis area (“msym”) and the horizontal part of the lower jaw branches (“hmr”), which may have been occupied by a stunted milk premolar (dp1).

The recent Dugong has a total of six molars in each half of its jaw in the course of its life , but not all of them perform their function at the same time. When the animal is born, only the second to fourth premolars (“p2” - “p4”) are usually present, which are the first to be worn out and which fail one after the other until the animal is around 8-16 years old. The premolars are gradually replaced by the molars ("m1" - "m3" / "M1" - "M3") further back in the jaw. The first premolar ("p2") usually fails at the age of 3–4 years, before the last molar ("m3" / "M3") has erupted from the jawbone. The two well-preserved lower jaws of Lentiarenium cristolii (OLL 1939/257 and OLL 2012/1) show a similar status with regard to the development of the molars. The alveoli of the premolars (“p2” - “p4”) are empty and all three molars (“m1” - “m3”) are already showing strong signs of wear. In contrast to Dugong dugon , in Lentiarenium cristolii there is another seventh molar between the fourth premolar (“p4”) and the first molar (“m1”), which is interpreted as a persistent milk premolar (“dp5”).

The premaxilla and the anterior part of the maxilla are missing from the fossil record. It is therefore not known whether the lentiarenium in the upper jaw had incisors that were elongated like tusks .

Paleecology

Recent dugong grazing seaweed

The "Linzer Sands" of the Linz-Melk Formation were deposited in the area of the north Alpine Molasse Basin on the northern edge of the Central Paratethys directly along the coast to the Bohemian Massif. They were formed during a transgression phase and represent deposits in the shallow marine area of lagoons , rocky coasts , sandy foreshore areas and areas of the shelf influenced by the tides .

The recent dugong inhabits similar habitats. It feeds mainly on seaweed , which it grazes on the seabed in shallow marine areas near the coast. A special adaptation to this diet is the typical front jaw area, which is bent downwards by around 70 °, which enables the animals to graze on the sea floor while swimming horizontally. The angle of the Lentiarenium, at approx. 60 °, is somewhat flatter than that of the Dugong, but a value of over 50 ° for fossil manatees is taken as an indication of a diet that is essentially the same as that of the recent Dugong.

Some fossil representatives of the fork-tailed manatees had tusk-like elongated incisors, which were probably used to dig up the carbohydrate-rich rhizomes of deeper-rooted seagrass species. The characteristic is usually associated with a lower jaw curvature than the recent Dugong, which can only accommodate shallow-rooted rhizomes. However, there is no corresponding fossil record for Lentiarenium , as the anterior areas of the upper jaw are not yet known.

Individual evidence

↑ ^a ^b ^c ^d LJ Fitzinger: Report on the fossil remains of a primeval sucker found in the sand camps of Linz (Halitherium Cristolii). In: Report on the Museum Francisco-Carolinum , Volume 6, 1842, pp. 61–72, ( digitized version ).
↑ ^a ^b ^c ^d ^e ^f ^g ^h M. Voss, B. Berning & E. Reiter: 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. In: European Journal of Taxonomy , Volume 256, 2016, pp. 1–32, ( pdf ).
↑ H. v. Meyer: Communications addressed to Professor Bronn. In: New Yearbook for Mineralogy, Geognosy, Geology and Petrefactology , year 1843, 1843, pp. 698–704, ( digitized version ).
↑ ^a ^b H. v. Meyer: Communications addressed to Professor Bronn. In: New yearbook for mineralogy, geognosy, geology and petrefactuality , year 1847, 1847, pp. 181–196, ( digitized version ).
↑ ^a ^b ^c ^d ^e ^f ^g ^h F. Spillmann: The sirens from the Oligocene of the Linz basin (Upper Austria) with explanations on "osteosclerosis" and "pachyostosis". In: Memoranda of the Austrian Academy of Sciences - Mathematical and Natural Science Class , Volume 110, 3rd treatise, 1959, 65 p., ( Digitized version ).
↑ ^a ^b C. Ehrlich: Contributions to the palaeontology and geognosy of Upper Austria and Salzburg: I. The fossil cetacean remains from the tertiary deposits near Linz, with special consideration of those of the Halianassa Collinii H. v. M., and the associated trunk skeleton found in August 1854. In: Report on the Museum Francisco-Carolinum , Volume 15, 1855, pp. 1–21, ( digitized version ).
^ ^A ^b F. Toula: Two mammal remains from the crystallized sandstone of Wallsee in Lower Austria and Perg in Upper Austria. In: New Yearbook for Mineralogy, Geology and Palaeontology , Supplement 12, Number 2, 1899, pp. 447–482.
↑ ^a ^b ^c O. Abel: The Sirens of the Mediterranean Tertiary Education in Austria. In: Abhandlungen der KK Geologische Reichsanstalt , Volume XIX, Number 2, 1904, pp. 1–223, ( digitized version ).
↑ ^a ^b ^c DP Domning: A Phylogenetic Analysis of the Sirenia. In: A. Berta & TA Deméré (Eds.): Contributions in Marine Mammal Paleontology Honoring Frank C. Withmore, Jr. - Proceedings of the San Diego Society of Natural History , Volume 29, 1994, pp. 177-189, ( digitized ).
^ M. Voss: On the invalidity of Halitherium schinzii Kaup, 1838 (Mammalia, Sirenia), with comments on systematic consequences. In: Zoosystematics and Evolution , Volume 90, Number 1, 2014, pp. 87-93, ( digitized version ).
↑ DP Domning: The earliest known fully quadrupedal sirenian. In: Nature , Volume 413, 2001, pp. 625-627, ( digitized ).
^ M. Voss & O. Hampe: Evidence for two sympatric sirenian species (Mammalia, Tethytheria) in the early Oligocene of Central Europe. In: Journal of Paleontology , Volume 91, Number 2, 2017, pp. 337-367, ( digitized ).
↑ U. Lehmann: Paleontological dictionary. 4th edition, Springer, Berlin / Heidelberg, 2014, ISBN 978-3-662-45605-7 , p. 190, ( reading sample ).
↑ DP Domning & P. Pervesler: The Sirenian Metaxytherium (Mammalia: Dugongidae) in the Badenian (Middle Miocene) of Central Europe. In: Austrian Journal of Earth Sciences , Volume 105, Number 3, 2012, pp. 125-160, ( digitized version ).
^ ^A ^b H. Marsh: Age Determination of the Dugong (Dugong dugon (Müller)) in Northern Australia and its Biological Implication. In: Report - International Whaling Commission , Special Issue 3, 1980, pp. 181-201, ( digitized version ).
^ MW Rasser, M. Harzhauser (coordinators) & 44 co-authors : Palaeogene and Neogene. In: T. McCann (Ed.): The Geology of Central Europe , Volume 2, The Geological Society of London, London, 2008, ISBN 978-1-86239-264-9 , p. 1056, ( digitized ).
^ BJ MacFadden, P. Higgins, MT Clementz & DS Jones: Diets, habitat preferences, and niche differentiation of Cenozoic sirenians from Florida: evidence from stable isotopes. In: Paleobiology , Volume 30, Number 2, 2002, pp. 297-324, ( digitized version ).
^ ^A ^b DP Domning: Sirenians, seagrasses, and Cenozoic ecological change in the Caribbean. In: Palaeogeography, Palaeoclimatology, Palaeoecology , Volume 166, 2001, pp. 27-50, ( digitized version ).

[Fitzinger,_1842-1] LJ Fitzinger: Report on the fossil remains of a primeval sucker found in the sand camps of Linz (Halitherium Cristolii). In: Report on the Museum Francisco-Carolinum , Volume 6, 1842, pp. 61–72, ( digitized version ).

[Voss_et_al.,_2016-2] ↑ ^a ^b ^c ^d ^e ^f ^g ^h M. Voss, B. Berning & E. Reiter: 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. In: European Journal of Taxonomy , Volume 256, 2016, pp. 1–32, ( pdf ).

[HvM,_1843-3] H. v. Meyer: Communications addressed to Professor Bronn. In: New Yearbook for Mineralogy, Geognosy, Geology and Petrefactology , year 1843, 1843, pp. 698–704, ( digitized version ).

[HvM,_1847-4] H. v. Meyer: Communications addressed to Professor Bronn. In: New yearbook for mineralogy, geognosy, geology and petrefactuality , year 1847, 1847, pp. 181–196, ( digitized version ).

[Spillmann,_1959-5] ↑ ^a ^b ^c ^d ^e ^f ^g ^h F. Spillmann: The sirens from the Oligocene of the Linz basin (Upper Austria) with explanations on "osteosclerosis" and "pachyostosis". In: Memoranda of the Austrian Academy of Sciences - Mathematical and Natural Science Class , Volume 110, 3rd treatise, 1959, 65 p., ( Digitized version ).

[Ehrlich,_1855-6] C. Ehrlich: Contributions to the palaeontology and geognosy of Upper Austria and Salzburg: I. The fossil cetacean remains from the tertiary deposits near Linz, with special consideration of those of the Halianassa Collinii H. v. M., and the associated trunk skeleton found in August 1854. In: Report on the Museum Francisco-Carolinum , Volume 15, 1855, pp. 1–21, ( digitized version ).

[Toula,_1899-7] A ^b F. Toula: Two mammal remains from the crystallized sandstone of Wallsee in Lower Austria and Perg in Upper Austria. In: New Yearbook for Mineralogy, Geology and Palaeontology , Supplement 12, Number 2, 1899, pp. 447–482.

[Abel,_1904-8] O. Abel: The Sirens of the Mediterranean Tertiary Education in Austria. In: Abhandlungen der KK Geologische Reichsanstalt , Volume XIX, Number 2, 1904, pp. 1–223, ( digitized version ).

[Domning,_1994-9] DP Domning: A Phylogenetic Analysis of the Sirenia. In: A. Berta & TA Deméré (Eds.): Contributions in Marine Mammal Paleontology Honoring Frank C. Withmore, Jr. - Proceedings of the San Diego Society of Natural History , Volume 29, 1994, pp. 177-189, ( digitized ).

[Voss,_2014-10] M. Voss: On the invalidity of Halitherium schinzii Kaup, 1838 (Mammalia, Sirenia), with comments on systematic consequences. In: Zoosystematics and Evolution , Volume 90, Number 1, 2014, pp. 87-93, ( digitized version ).

[Domning,_2001-11] DP Domning: The earliest known fully quadrupedal sirenian. In: Nature , Volume 413, 2001, pp. 625-627, ( digitized ).

[Voss_&_Hampe,_2017-12] M. Voss & O. Hampe: Evidence for two sympatric sirenian species (Mammalia, Tethytheria) in the early Oligocene of Central Europe. In: Journal of Paleontology , Volume 91, Number 2, 2017, pp. 337-367, ( digitized ).

[Lehmann,_2014-13] U. Lehmann: Paleontological dictionary. 4th edition, Springer, Berlin / Heidelberg, 2014, ISBN 978-3-662-45605-7 , p. 190, ( reading sample ).

[Domning_&_Pervesler,_2012-14] DP Domning & P. Pervesler: The Sirenian Metaxytherium (Mammalia: Dugongidae) in the Badenian (Middle Miocene) of Central Europe. In: Austrian Journal of Earth Sciences , Volume 105, Number 3, 2012, pp. 125-160, ( digitized version ).

[Marsh,_1980-15] A ^b H. Marsh: Age Determination of the Dugong (Dugong dugon (Müller)) in Northern Australia and its Biological Implication. In: Report - International Whaling Commission , Special Issue 3, 1980, pp. 181-201, ( digitized version ).

[Rasser_&_Harzhauser,_2008-16] MW Rasser, M. Harzhauser (coordinators) & 44 co-authors : Palaeogene and Neogene. In: T. McCann (Ed.): The Geology of Central Europe , Volume 2, The Geological Society of London, London, 2008, ISBN 978-1-86239-264-9 , p. 1056, ( digitized ).

[MacFadden_et_al.,_2004-17] BJ MacFadden, P. Higgins, MT Clementz & DS Jones: Diets, habitat preferences, and niche differentiation of Cenozoic sirenians from Florida: evidence from stable isotopes. In: Paleobiology , Volume 30, Number 2, 2002, pp. 297-324, ( digitized version ).

[Domning,_2001b-18] A ^b DP Domning: Sirenians, seagrasses, and Cenozoic ecological change in the Caribbean. In: Palaeogeography, Palaeoclimatology, Palaeoecology , Volume 166, 2001, pp. 27-50, ( digitized version ).