A recent cladistic analysis of Hoplitomeryx, the mysterious ruminants from the Abruzzo-Apulian Platform (central- and south-eastern Italy), was based on a character-taxon matrix of 121 features (48 cranial, 51 dental and 22 postcranial characters). The matrix was set up based on direct observation and the literature, to infer the interrelationships between Hoplitomerycidae and an ingroup of twelve past and six living ruminant taxa. The type specimens had been found in the 1970’s in karstic fissure fillings, most likely of Messinian age, in the Gargano promontory (Apulia, southeastern Italy). During the 1990’s a rich amount of Hoplitomeryx remains were discovered in Lower Tortonian layered calcarenites outcropping near Scontrone (Abruzzo, central Italy). Hoplitomerycids had originally been linked more closely with Cervids, and thus accommodated in the Cervoidea, only for their possessing two lacrimal orifices and closed metatarsal gulleys. The cladistic analysis stems hoplitomerycids either between antilocaprids and bovids, or antilocaprids and giraffids. They can be the sister group of two clades, one including Bovidae, Cervidae, Moschidae, and Palaeomerycidae, the other formed by Antilocapridae, Giraffidae, and Climacoceridae. Contrary to what is normally believed, they were not found to be linked directly with cervids, despite their possessing two lacrimal orifices and closed metatarsal gulleys. But these characters are possessed also by numerous other ruminants. Because of its sharing an assortment of characters with many other ruminants, Hoplitomerycidae is believed to be descendant of a primitive ruminant stock that should be placed somewhere at the basal divergence of Pecora. Geological evidence from Abruzzo-Apulia to far off the Adriatic shore shows that 29-30 Ma the Abruzzo-Apulia platform was connected with the Balkans by a stripe of land across the Adriatic Sea, approximately where the Tremiti islands are today. The forerunners of Hoplitomeryx spread into Abruzzo-Apulia from the Balkans crossing this trans- Adriatic landbridge. Then the land connection sank, leaving the ruminants isolated for a few million years. Living in insularity hoplitomerycids thus radiated into a variety of species, developing autapomorphic homoplasies that masquerade as homologies which near them to antilocaprids and bovids, or even to giraffids, rather than to cervids, as previously believed. For this reason they cannot be easily accommodated in any of the superfamilies of higher ruminants. But the point is: who were the ancestors of these weird ruminants? Character polarities are obscured by hoplitomerycids’ already advanced endemic transformations and are therefore problematic to establish. Comparative and developmental morphology may nonetheless assist in pinpointing plesiomorphies that contribute to the identification of the family’s potential forerunners, to the reconstruction of its true history, as well as to the detection of its possible area of provenance. Comparisons with Tragulina and higher ruminants show that hoplitomerycids display mosaic evolution, combining primitive cranial characters with fairly advanced dental and postcranial traits. This is not surprising, considering the quite more intense adaptive pressures to which teeth and limbs are exposed compared to skulls. Hoplitomerycids’ cranial plesiomorphies are therefore preserved traces of their past which can be pursued to track their ancestry. Preliminary results seem leading somewhere towards Early Oligocene Tragulina, possibly Gelocidae or Lophiomerycidae. These potential ancestral taxa were dispersed in Eurasia when two favorable paleogeographical circumstances were met for the colonization of the Abruzzo-Apulian area: 1) the formation of the trans-Adriatic landbridge; 2) the almost complete isolation of Paratethys, which was linked to the Mediterranean only in the far west, and to the North Sea through the Rhine Graben. Hence, landways formed for a limited time period connecting the Abruzzo-Apulia paleoprovince with both eastern European and Asian areas.

Hoplitomerycidae (Ruminantia, central-southeastern Italy): whom from? / Mazza P.. - STAMPA. - (2012), pp. 89-90. (Intervento presentato al convegno RCMNS Interim Colloquium Paratethys-Mediterranean Interactions: Environmental Crises during the Neogene tenutosi a Bucarest nel 27-30 September 2012).

Hoplitomerycidae (Ruminantia, central-southeastern Italy): whom from?

MAZZA, PAUL
2012

Abstract

A recent cladistic analysis of Hoplitomeryx, the mysterious ruminants from the Abruzzo-Apulian Platform (central- and south-eastern Italy), was based on a character-taxon matrix of 121 features (48 cranial, 51 dental and 22 postcranial characters). The matrix was set up based on direct observation and the literature, to infer the interrelationships between Hoplitomerycidae and an ingroup of twelve past and six living ruminant taxa. The type specimens had been found in the 1970’s in karstic fissure fillings, most likely of Messinian age, in the Gargano promontory (Apulia, southeastern Italy). During the 1990’s a rich amount of Hoplitomeryx remains were discovered in Lower Tortonian layered calcarenites outcropping near Scontrone (Abruzzo, central Italy). Hoplitomerycids had originally been linked more closely with Cervids, and thus accommodated in the Cervoidea, only for their possessing two lacrimal orifices and closed metatarsal gulleys. The cladistic analysis stems hoplitomerycids either between antilocaprids and bovids, or antilocaprids and giraffids. They can be the sister group of two clades, one including Bovidae, Cervidae, Moschidae, and Palaeomerycidae, the other formed by Antilocapridae, Giraffidae, and Climacoceridae. Contrary to what is normally believed, they were not found to be linked directly with cervids, despite their possessing two lacrimal orifices and closed metatarsal gulleys. But these characters are possessed also by numerous other ruminants. Because of its sharing an assortment of characters with many other ruminants, Hoplitomerycidae is believed to be descendant of a primitive ruminant stock that should be placed somewhere at the basal divergence of Pecora. Geological evidence from Abruzzo-Apulia to far off the Adriatic shore shows that 29-30 Ma the Abruzzo-Apulia platform was connected with the Balkans by a stripe of land across the Adriatic Sea, approximately where the Tremiti islands are today. The forerunners of Hoplitomeryx spread into Abruzzo-Apulia from the Balkans crossing this trans- Adriatic landbridge. Then the land connection sank, leaving the ruminants isolated for a few million years. Living in insularity hoplitomerycids thus radiated into a variety of species, developing autapomorphic homoplasies that masquerade as homologies which near them to antilocaprids and bovids, or even to giraffids, rather than to cervids, as previously believed. For this reason they cannot be easily accommodated in any of the superfamilies of higher ruminants. But the point is: who were the ancestors of these weird ruminants? Character polarities are obscured by hoplitomerycids’ already advanced endemic transformations and are therefore problematic to establish. Comparative and developmental morphology may nonetheless assist in pinpointing plesiomorphies that contribute to the identification of the family’s potential forerunners, to the reconstruction of its true history, as well as to the detection of its possible area of provenance. Comparisons with Tragulina and higher ruminants show that hoplitomerycids display mosaic evolution, combining primitive cranial characters with fairly advanced dental and postcranial traits. This is not surprising, considering the quite more intense adaptive pressures to which teeth and limbs are exposed compared to skulls. Hoplitomerycids’ cranial plesiomorphies are therefore preserved traces of their past which can be pursued to track their ancestry. Preliminary results seem leading somewhere towards Early Oligocene Tragulina, possibly Gelocidae or Lophiomerycidae. These potential ancestral taxa were dispersed in Eurasia when two favorable paleogeographical circumstances were met for the colonization of the Abruzzo-Apulian area: 1) the formation of the trans-Adriatic landbridge; 2) the almost complete isolation of Paratethys, which was linked to the Mediterranean only in the far west, and to the North Sea through the Rhine Graben. Hence, landways formed for a limited time period connecting the Abruzzo-Apulia paleoprovince with both eastern European and Asian areas.
2012
Paratethys-Mediterranean Interactions Environmental Crises during the Neogene
RCMNS Interim Colloquium Paratethys-Mediterranean Interactions: Environmental Crises during the Neogene
Bucarest
Mazza P.
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