Topic
Romundina
About: Romundina is a research topic. Over the lifetime, 5 publications have been published within this topic receiving 131 citations.
Papers
TL;DR: ‘supragnathal’ toothplates from the acanthothoracid placoderm Romundina stellina comprise multi-cuspid teeth, each composed of an enameloid cap and core of dentine, which suggests that it has been lost in other placoderms.
Abstract: Theories on the origin of vertebrate teeth have long focused on chondrichthyans as reflecting a primitive condition—but this is better informed by the extinct placoderms, which constitute a sister clade or grade to the living gnathostomes. Here, we show that ‘supragnathal’ toothplates from the acanthothoracid placoderm Romundina stellina comprise multi-cuspid teeth, each composed of an enameloid cap and core of dentine. These were added sequentially, approximately circumferentially, about a pioneer tooth. Teeth are bound to a bony plate that grew with the addition of marginal teeth. Homologous toothplates in arthrodire placoderms exhibit a more ordered arrangement of teeth that lack enameloid, but their organization into a gnathal, bound by layers of cellular bone associated with the addition of each successional tooth, is the same. The presence of enameloid in the teeth of Romundina suggests that it has been lost in other placoderms. Its covariation in the teeth and dermal skeleton of placoderms suggests a lack of independence early in the evolution of jawed vertebrates. It also appears that the dentition—manifest as discrete gnathal ossifications—was developmentally discrete from the jaws during this formative episode of vertebrate evolution.
35 citations
TL;DR: Prerostral anatomy of the small acanthothoracid Romundina stellina, one of the earliest and most basal placoderms, is presented for the first time, providing important clues to the growth modes and biology of the animal.
17 citations
TL;DR: In this paper, a disarticulated element was identified as a dental plate of the acanthothoracid Romundina stellina, with synchrotron microtomography providing characters to comment on ongoing debates regarding the evolution of teeth.
Abstract: Placoderms (Devonian fossil fishes) are resolved phylogenetically to the base of jawed vertebrates and provide important evidence for evolutionary origins of teeth, particularly with respect to the Arthrodira. The arthrodires represent a derived group of placoderms; the dentition of other more primitive placoderms such as the acanthothoracids is less well known. Articulated acanthothoracid dental plates are rare; x-ray computed tomography of a single, unique specimen, along with 3D segmentation of bone, oral denticles and vascular spaces, provides intrinsic developmental and topological information relevant to tooth origins. Recently, a disarticulated element was identified as a dental plate of the acanthothoracid Romundina stellina, with synchrotron microtomography providing characters to comment on ongoing debates regarding the evolution of teeth. We used segmental quantitative methods to re-analyse this data, for comparison to the articulated and unquestionable acanthothoracid dental plates above. We demonstrate substantial differences between these, disputing the identity of the isolated plate of R. stellina as a dental plate, and thus its relevance to questions of tooth evolution.
8 citations
TL;DR: A gnathal plate from the acanthothoracid Romundina stellina comprises marginally more teeth than expected and is shown to be derived from the earliest jawed vertebrates, the extinct placoderms.
Abstract: Establishing the evolutionary origins of teeth is difficult not least since researchers disagree on whether or not the earliest jawed vertebrates, the extinct placoderms, possessed teeth. We recently showed that a gnathal plate from the acanthothoracid Romundina stellina comprises marginally added
5 citations
Book Chapter•
1 Jan 2004
TL;DR: It is proposed that two median dorsal plates may be primitive for placoderms, this being the defining difference to the osteichthyan shoulder girdle in creating a rigid ring of bones for the placoderm dermal neckjoint.
Abstract: New specimens of acanthothoracid placoderms and related forms (Romundina, Murrindalaspis, Brindabellaspis) are described, illustrating aspects of placoderm anatomy in the assumed basal branch according to a working hypothesis of placoderm interrelationships. It is proposed that two median dorsal plates may be primitive for placoderms, this being the defining difference to the osteichthyan shoulder girdle in creating a rigid ring of bones for the placoderm dermal neckjoint. One pectoral fin articulation, an anterior insertion for the internal rectus extra ocular muscle, and two abducens innervated eye muscles, may be primitive for placoderms, and for the Gnathostomata.
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2017 | 1 |
| 2016 | 1 |
| 2015 | 1 |
| 2010 | 1 |
| 2004 | 1 |