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This study presents a comprehensive taxonomic revision of the family Suberitidae (Porifera: Demospongiae) for California, USA. We include the three species previously known from the region, document two additional species previously known from other regions, and formally describe four new species as Pseudosuberites latke sp. nov., Suberites californiana sp. nov., Suberites kumeyaay sp. nov., and Suberites agaricus sp. nov. Multi-locus DNA sequence data is presented for seven of the nine species, and was combined with all publicly available data to produce the most comprehensive global phylogeny for the family to date. By integrating morphological and genetic data, we show that morphological characters may be sufficient for regional species identification but are likely inadequate for global classification into genera that reflect the evolutionary history of the family. We therefore propose that DNA sequencing is a critical component to support future taxonomic revisions. 

The methane seeps on the Pacific margin of Costa Rica support extensive animal diversity and offer insights into deep-sea biogeography. During five expeditions between 2009 and 2019, we conducted intensive faunal sampling via 63 submersible dives to 11 localities at depths of 300–3600 m. Based on these expeditions and published literature, we compiled voucher specimens, images, and 274 newly published DNA sequences to present a taxonomic inventory of macrofaunal and megafaunal diversity with a focus on invertebrates. In total 488 morphospecies were identified, representing the highest number of distinct morphospecies published from a single seep or vent region to date. Of these, 131 are described species, at least 58 are undescribed species, and the remainder include some degree of taxonomic uncertainty, likely representing additional undescribed species. Of the described species, 38 are known only from the Costa Rica seeps and their vicinity. Fifteen range extensions are also reported for species known from Mexico, the Galápagos seamounts, Chile, and the western Pacific; as well as 16 new depth records and three new seep records for species known to occur at vents or organic falls. No single evolutionary narrative explains the patterns of biodiversity at these seeps, as even morphologically indistinguishable species can show different biogeographic affinities, biogeographic ranges, or depth ranges. The value of careful molecular taxonomy and comprehensive specimen-based regional inventories is emphasized for biodiversity research and monitoring. 

Sea cucumbers (Holothuroidea) are a diverse clade of echinoderms found from intertidal waters to the bottom of the deepest oceanic trenches. Their reduced skeletons and limited number of phylogenetically informative traits have long obfuscated morphological classifications. Sanger-sequenced molecular datasets have also failed to constrain the position of major lineages. Noteworthy, topological uncertainty has hindered a resolution for Neoholothuriida, a highly diverse clade of Permo-Triassic age. We perform the first phylogenomic analysis of Holothuroidea, combining existing datasets with 13 novel transcriptomes. Using a highly curated dataset of 1100 orthologues, our efforts recapitulate previous results, struggling to resolve interrelationships among neoholothuriid clades. Three approaches to phylogenetic reconstruction (concatenation under both site-homogeneous and site-heterogeneous models, and coalescent-aware inference) result in alternative resolutions, all of which are recovered with strong support and across a range of datasets filtered for phylogenetic usefulness. We explore this intriguing result using gene-wise log-likelihood scores and attempt to correlate these with a large set of gene properties. While presenting novel ways of exploring and visualizing support for alternative trees, we are unable to discover significant predictors of topological preference, and our efforts fail to favour one topology. Neoholothuriid genomes seem to retain an amalgam of signals derived from multiple phylogenetic histories. 

Stomatopoda, commonly known as mantis shrimps, are notable for their enlarged second maxillipeds encompassing the raptorial claw. The form of the claw can be used to divide them into two basic groups: smashers and spearers. Previous phylogenetic studies of Stomatopoda have focused on morphology or a few genes, though there have been whole mitochondrial genomes published for 15 members of Stomatopoda. However, the sampling has been somewhat limited with key taxa not included. Here, nine additional stomatopod mitochondrial genomes were generated and combined with the other available mitogenomes for a phylogenetic analysis. We used the 13 protein coding genes, as well as 12S rRNA, 16S rRNA genes, and included nuclear 18S rRNA gene sequences. Different rooting options were used for the analyses: (1) single and multiple outgroups from various eumalocostracan relatives and (2) a stomatopod-only dataset, with Hemisquilla californiensis used to root the topologies, based on the current hypothesis that Hemisquilla is the sister group to the rest of Stomatopoda. The eumalocostracan-rooted analyses all showed H. californiensis nested within Stomatopoda, raising doubts as to previous hypotheses as to its placement. Allowing for the rooting difference, the H. californiensis outgroup datasets had the same tree topology as the eumalocostracan outgroup datasets with slight variation at poorly supported nodes. Of the major taxonomic groupings sampled to date, Squilloidea was generally found to be monophyletic while Gonodactyloidea was not. The position of H. californiensis was found inside its superfamily, Gonodactyloidea, and grouped in a weakly supported clade containing Odontodactylus havanensis and Lysiosquillina maculata for the eumalocostracan-rooted datasets. An ancestral state reconstruction was performed on the raptorial claw form and provides support that spearing is the ancestral state for extant Stomatopoda, with smashing evolving subsequently one or more times. 

Continental margins host methane seeps, animal falls and wood falls, with chemosynthetic communities that may share or exchange species. The goal of this study was to examine the existence and nature of linkages among chemosynthesis-based ecosystems by deploying organic fall mimics (bone and wood) alongside defaunated carbonate rocks within high and lesser levels of seepage activity for 7.4 years. We compared community composition, density, and trophic structure of invertebrates on these hard substrates at active methane seepage and transition (less seepage) sites at Mound 12 at ~1,000 m depth, a methane seep off the Pacific coast of Costa Rica. At transition sites, the community composition on wood and bone was characteristic of natural wood- and whale-fall community composition, which rely on decay of the organic substrates. However, at active sites, seepage activity modified the relationship between fauna and substrate, seepage activity had a stronger effect in defining and homogenizing these communities and they depend less on organic decay. In contrast to community structure, macrofaunal trophic niche overlap between substrates, based on standard ellipse areas, was greater at transition sites than at active sites, except between rock and wood. Our observations suggest that whale- and wood-fall substrates can function as stepping stones for seep fauna even at later successional stages, providing hard substrate for attachment and chemosynthetic food. 

The bathyal serpulid Laminatubus alvini ten Hove & Zibrowius, 1986 was described from the periphery of hydrothermal vents of the Galapagos Rift and has been recorded from other vent communities of the East Pacific Rise (EPR). Here we assessed the biodiversity of serpulids collected from eastern Pacific hydrothermal vents and methane seeps using DNA sequences and morphology. Laminatubus alvini showed little genetic variation over a wide geographic range from the Alarcon Rise vents in southern Gulf of California (~23°N), to at least a point at 38°S on the EPR. Specimens from several methane seeps off Costa Rica and the Gulf of California (Mexico) differed markedly from those of Laminatubus alvini on DNA sequence data and in having seven thoracic chaetigers and lacking Spirobranchus-type special collar chaetae, thus fitting the diagnosis of Neovermilia. However, phylogenetic analysis of molecular data showed that L. alvini and the seep specimens form a well-supported clade. Moreover, among the seep specimens there was minimally a ~7% distance in mitochondrial cytochrome b sequences between a shallow-water (1000 m) seep clade restricted to Costa Rica and a deep-water clade (1800 m) from Costa Rica to Gulf of California. We describe the seep taxa here as morphologically indistinguishable L. paulbrooksi n. sp. and L. joycebrooksae n. sp. 

Echinoids are key components of modern marine ecosystems. Despite a remarkable fossil record, the emergence of their crown group is documented by few specimens of unclear affinities, rendering their early history uncertain. The origin of sand dollars, one of its most distinctive clades, is also unclear due to an unstable phylogenetic context. We employ 18 novel genomes and transcriptomes to build a phylogenomic dataset with a near-complete sampling of major lineages. With it, we revise the phylogeny and divergence times of echinoids, and place their history within the broader context of echinoderm evolution. We also introduce the concept of a chronospace – a multidimensional representation of node ages – and use it to explore methodological decisions involved in time calibrating phylogenies. We find the choice of clock model to have the strongest impact on divergence times, while the use of site-heterogeneous models and alternative node prior distributions show minimal effects. The choice of loci has an intermediate impact, affecting mostly deep Paleozoic nodes, for which clock-like genes recover dates more congruent with fossil evidence. Our results reveal that crown group echinoids originated in the Permian and diversified rapidly in the Triassic, despite the relative lack of fossil evidence for this early diversification. We also clarify the relationships between sand dollars and their close relatives and confidently date their origins to the Cretaceous, implying ghost ranges spanning approximately 50 million years, a remarkable discrepancy with their rich fossil record.