Caron & Moysiuk

https://royalsocietypublishing.org/doi/10.1098/rsos.210664

Open source (at least for now)

Abstract

Radiodonts, stem-group euarthropods that evolved during the Cambrian explosion, were among the largest and most diversified lower palaeozoic predators.. These animals were widespread geographically, occupying a variety of ecological niches, from benthic foragers to nektonic suspension feeders and apex predators. Here, we describe the largest Cambrian hurdiid radiodont known so far, Titanokorys gainesi, gen. et sp. nov., from the Burgess Shale (Marble Canyon, Kootenay National Park, British Columbia). Estimated to reach half a metre in length, this new species bears a very large ovoid-shaped central carapace with distinct short posterolateral processes and an anterior spine. Geometric morphometric analyses highlight the high diversity of carapace shapes in hurdiids and show that Titanokorys bridges a morphological gap between forms with long and short carapaces. Carapace shape, however, is prone to homoplasy and shows no consistent relationship with trophic ecology, as demonstrated by new data, including a reappraisal of the poorly known Pahvantia. Despite distinct carapaces, Titanokorys shares similar rake-like appendages for sediment-sifting with Cambroraster, a smaller but much more abundant sympatric hurdiid from the Burgess Shale. The co-occurrence of these two species on the same bedding planes highlights potential competition for benthic resources and the high diversity of large predators sustained by Cambrian communities.

"Radiodonts" include the more well-known Anomalocaridids, known for several decades, and have been discovered to include many other "large"
(~ meter) Cambrian predators. This one is remarkable for the size of its carapace.

On 9/8/21 8:38 AM, erik simpson wrote:
> Caron & Moysiuk
>
> https://royalsocietypublishing.org/doi/10.1098/rsos.210664
>
> Open source (at least for now)
>
> Abstract
>
> Radiodonts, stem-group euarthropods that evolved during the Cambrian explosion, were among the largest and most diversified lower palaeozoic predators. These animals were widespread geographically, occupying a variety of ecological niches, from benthic foragers to nektonic suspension feeders and apex predators. Here, we describe the largest Cambrian hurdiid radiodont known so far, Titanokorys gainesi, gen. et sp. nov., from the Burgess Shale (Marble Canyon, Kootenay National Park, British Columbia). Estimated to reach half a metre in length, this new species bears a very large ovoid-shaped central carapace with distinct short posterolateral processes and an anterior spine. Geometric morphometric analyses highlight the high diversity of carapace shapes in hurdiids and show that Titanokorys bridges a morphological gap between forms with long and short carapaces. Carapace shape, however, is prone to homoplasy and shows no consistent relationship with trophic ecology, as demonstrated by new data, including a reappraisal of the poorly known Pahvantia. Despite distinct carapaces, Titanokorys shares similar rake-like appendages for sediment-sifting with Cambroraster, a smaller but much more abundant sympatric hurdiid from the Burgess Shale. The co-occurrence of these two species on the same bedding planes highlights potential competition for benthic resources and the high diversity of large predators sustained by Cambrian communities.
>
> "Radiodonts" include the more well-known Anomalocaridids, known for several decades, and have been discovered to include many other "large"
> (~ meter) Cambrian predators. This one is remarkable for the size of its carapace.
>
Interesting stuff, though I'm disappointed that the paper doesn't
include a phylogenetic analysis to show where this all fits in the
context of radiodonts or stem-arthropods or "lobopods" in general.

On Wednesday, September 8, 2021 at 8:48:00 AM UTC-7, John Harshman wrote:
> On 9/8/21 8:38 AM, erik simpson wrote:
> > Caron & Moysiuk
> >
> > https://royalsocietypublishing.org/doi/10.1098/rsos.210664
> >
> > Open source (at least for now)
> >
> > Abstract
> >
> > Radiodonts, stem-group euarthropods that evolved during the Cambrian explosion, were among the largest and most diversified lower palaeozoic predators. These animals were widespread geographically, occupying a variety of ecological niches, from benthic foragers to nektonic suspension feeders and apex predators. Here, we describe the largest Cambrian hurdiid radiodont known so far, Titanokorys gainesi, gen. et sp. nov., from the Burgess Shale (Marble Canyon, Kootenay National Park, British Columbia). Estimated to reach half a metre in length, this new species bears a very large ovoid-shaped central carapace with distinct short posterolateral processes and an anterior spine. Geometric morphometric analyses highlight the high diversity of carapace shapes in hurdiids and show that Titanokorys bridges a morphological gap between forms with long and short carapaces. Carapace shape, however, is prone to homoplasy and shows no consistent relationship with trophic ecology, as demonstrated by new data, including a reappraisal of the poorly known Pahvantia. Despite distinct carapaces, Titanokorys shares similar rake-like appendages for sediment-sifting with Cambroraster, a smaller but much more abundant sympatric hurdiid from the Burgess Shale. The co-occurrence of these two species on the same bedding planes highlights potential competition for benthic resources and the high diversity of large predators sustained by Cambrian communities.
> >
> > "Radiodonts" include the more well-known Anomalocaridids, known for several decades, and have been discovered to include many other "large"
> > (~ meter) Cambrian predators. This one is remarkable for the size of its carapace.
> >
> Interesting stuff, though I'm disappointed that the paper doesn't
> include a phylogenetic analysis to show where this all fits in the
> context of radiodonts or stem-arthropods or "lobopods" in general.

So far as I'm aware, the Wikipedia entry on Radiodonta https://en.wikipedia..org/wiki/Radiodonta is
still a good summary of the stem arthropod situation. There are polytomies galore.