Pluridens imelaki, new giant halisaurine mosasaur from Morocco + Caimaninae and alligatoroid clades + Toxicofera clade support
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Ben Creisler
Mar 5, 2026, 1:32:03 PM (8 days ago) Mar 5
to DinosaurMa...@googlegroups.com
Ben Creisler
Pluridens imelaki sp. nov.
Nicholas R. Longrich and Nour-Eddine Jalil (2026)
A Giant Halisaurine from the Late Maastrichtian of Morocco
Diversity 18(3): 159;
doi: https://doi.org/10.3390/d18030159
https://www.mdpi.com/1424-2818/18/3/159
The Late Cretaceous deposits of Morocco have yielded one of the richest and most diverse assemblages of marine reptiles in the world, with the mosasaurids representing the dominant group. Among the most common mosasaurs are members of the subfamily Halisaurinae. Halisaurines ranged in size from the relatively small Halisaurus, which reached 4–5 m in length, to the larger Pluridens serpentis, which may have reached 7.5 m in length. Here we report a new, giant species of Pluridens, Pluridens imelaki. The new Pluridens is characterized by a slender, rectangular snout, a T-shaped premaxilla–maxilla junction, interlocking premaxilla–maxilla joint, a prominent dorsal ridge on the premaxilla, an exceptionally long and slender mandible, a tooth count of ~25 dentary teeth, straight, triangular tooth crowns that are strongly bent back just above the tooth–root junction, a low coronoid process and a tall and slender retroarticular process. The skull is 1.25 m long, suggesting a body length of ~9 m or more, comparable in size to large predators such as Thalassotitan. Differences between P. imaleki and P. serpentis in the jaw and tooth structure, eye size and innervation of the rostrum, as well as overall size, suggest they had different foraging strategies and occupied distinct ecological niches. Pluridens imelaki reveals that Halisaurinae were not only more species-rich than previously recognized, but also exhibited greater diversity in tooth morphology, jaw shape, and body size than previously thought. Rather than simply being outcompeted by Mosasaurinae, the Halisaurinae staged a minor adaptive radiation in the Late Cretaceous and were important members of the ecosystem in low latitudes. Pluridens imelaki appears to have been exceptionally rare in the phosphates, being documented by only a single specimen among the many hundreds of mosasaur remains recovered over many years. This underscores how the species richness of the phosphates and other diverse assemblages is driven by rare taxa that are only revealed through extensive sampling.
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Bottosauria (new clade name), Caimanini (new clade name), Purussauria (new clade name), Purussauridae (new clade name)
Giovanne M. Cidade, Pedro L. Godoy, Patricia Amavet, Adam Cossette, Andrés Solórzano, Paula Bona, Mónica Angulo-Bedoya, Sergio A. Balaguera-Reina, Márton Rabi, Izeni Pires-Farias, Rodrigo G. Figueiredo, Martin D. Ezcurra, Pedro S. Bittencourt, Christopher A. Brochu & Igor J. Roberto (2026)
The phylogenetic nomenclature of Caimaninae (Crocodylia: Alligatoroidea)
Historical Biology (advance online publication)
doi: https://doi.org/10.1080/08912963.2026.2614968
https://www.tandfonline.com/doi/full/10.1080/08912963.2026.2614968
Caimaninae is one of the main clades within alligatoroid crocodylians. Its extant diversity encompasses six species in three genera – Caiman, Melanosuchus and Paleosuchus – and is largely native to South America; the fossil record, in contrast, reveals a far greater diversity, extending from the Late Cretaceous and, although concentrated in South America, also showing notable fossils from Central America, North America and the Caribbean. Systematic and taxonomic research on Caimaninae began in the 18th century, with phylogenetic-based systematics, taxonomy and nomenclature being applied since the 1980s. Following the publication of the International Code of Phylogenetic Nomenclature (PhyloCode), a cojoined effort by Caimaninae systematists to standardise the phylogenetic systematics and nomenclature of the group was required, which is the objective of this paper. Herein, we provide phylogenetic definitions for seven clade names: Caimaninae, Bottosauria (new clade name), Caimanini (new clade name), Jacarea, Purussauria (new clade name), Purussauridae (new clade name) and Nettosuchidae. Detailed information on each clade is provided, including taxonomic and evolutionary history, composition, fossil record, divergence dates, characteristics and previous phylogenetic studies. Our intention with this effort is to provide a stable framework on which to base further research on the diversity of the group at several levels, and to encourage the use of phylogenetic nomenclature in Crocodylia.
Free pdf:
Magnus Wolf, Axel Janke & Krister T. Smith (2026)
The genome of the relict earless monitor lizard, Lanthanotus borneensis, and the Toxicofera hypothesis
BMC Biology 24: 58
doi: https://doi.org/10.1186/s12915-026-02552-4
https://link.springer.com/article/10.1186/s12915-026-02552-4
Background
The earless monitor lizard, Lanthanotus borneensis, is a unique living fossil restricted to the island of Borneo and a possible key to understanding the evolution of the venom delivery system and secondary adaptation to water in lizards and snakes (Squamata).
Results
We sequenced and de novo assembled the genome of L. borneensis to a total size of 1.5 Gbp, 975 contigs with an N50 of 52 Mbp and an L50 of 9. The genome completeness is estimated to be 93% based on the Sauropsida OrthoDB core gene set. A genome-wide set of Lepidosauria orthologs was compiled to reconstruct and date their phylogeny, resulting in 966 protein-coding sequences amounting to a concatenated alignment of 356 kbp with 188 kbp parsimony-informative sites. Based on this phylogenomic analysis, one of the largest of its kind yet conducted for Squamata, we identified that a Toxicofera clade (comprising Serpentes, Anguimorpha, and Iguania) is supported by a plurality of gene trees, but critically, support for relationships within Toxicofera is almost equally distributed amongst the three possible topologies. Our tree-dating confirms a rapid divergence of all major squamate clades within the first 10% of squamate history, which may have contributed to rampant incomplete lineage sorting. While we did not identify positive selection on genes associated with venom components at the base of Toxicofera, our analyses found strong positive selection on the giant protein titin throughout the main clades of Toxicofera and especially in snakes. Genome-wide heterozygosity is low (HO = 0.0004), as is the effective population size towards the present.
Conclusions
Future studies of the evolution of the venom delivery system in Toxicofera require a “true” species tree but also individual gene trees due to incomplete lineage sorting and the concomitant potential for hemiplasy. Titin—a key component of striated muscle elasticity—emerges as a target for future evolutionary studies in Toxicofera and especially in wide-gaped snakes (“Macrostomata”). The low observed genome-wide heterozygosity and the low but stable effective population size of L. borneensis during the large-scale habitat fluctuations on Sundaland in the Quaternary suggest an unexpected resilience to environmental perturbations but also a potentially lowered adaptive potential of this isolated lineage.
New reptile papers:
Free pdf:
Pluridens imelaki sp. nov.
Nicholas R. Longrich and Nour-Eddine Jalil (2026)
A Giant Halisaurine from the Late Maastrichtian of Morocco
Diversity 18(3): 159;
doi: https://doi.org/10.3390/d18030159
https://www.mdpi.com/1424-2818/18/3/159
The Late Cretaceous deposits of Morocco have yielded one of the richest and most diverse assemblages of marine reptiles in the world, with the mosasaurids representing the dominant group. Among the most common mosasaurs are members of the subfamily Halisaurinae. Halisaurines ranged in size from the relatively small Halisaurus, which reached 4–5 m in length, to the larger Pluridens serpentis, which may have reached 7.5 m in length. Here we report a new, giant species of Pluridens, Pluridens imelaki. The new Pluridens is characterized by a slender, rectangular snout, a T-shaped premaxilla–maxilla junction, interlocking premaxilla–maxilla joint, a prominent dorsal ridge on the premaxilla, an exceptionally long and slender mandible, a tooth count of ~25 dentary teeth, straight, triangular tooth crowns that are strongly bent back just above the tooth–root junction, a low coronoid process and a tall and slender retroarticular process. The skull is 1.25 m long, suggesting a body length of ~9 m or more, comparable in size to large predators such as Thalassotitan. Differences between P. imaleki and P. serpentis in the jaw and tooth structure, eye size and innervation of the rostrum, as well as overall size, suggest they had different foraging strategies and occupied distinct ecological niches. Pluridens imelaki reveals that Halisaurinae were not only more species-rich than previously recognized, but also exhibited greater diversity in tooth morphology, jaw shape, and body size than previously thought. Rather than simply being outcompeted by Mosasaurinae, the Halisaurinae staged a minor adaptive radiation in the Late Cretaceous and were important members of the ecosystem in low latitudes. Pluridens imelaki appears to have been exceptionally rare in the phosphates, being documented by only a single specimen among the many hundreds of mosasaur remains recovered over many years. This underscores how the species richness of the phosphates and other diverse assemblages is driven by rare taxa that are only revealed through extensive sampling.
=====
Bottosauria (new clade name), Caimanini (new clade name), Purussauria (new clade name), Purussauridae (new clade name)
Giovanne M. Cidade, Pedro L. Godoy, Patricia Amavet, Adam Cossette, Andrés Solórzano, Paula Bona, Mónica Angulo-Bedoya, Sergio A. Balaguera-Reina, Márton Rabi, Izeni Pires-Farias, Rodrigo G. Figueiredo, Martin D. Ezcurra, Pedro S. Bittencourt, Christopher A. Brochu & Igor J. Roberto (2026)
The phylogenetic nomenclature of Caimaninae (Crocodylia: Alligatoroidea)
Historical Biology (advance online publication)
doi: https://doi.org/10.1080/08912963.2026.2614968
https://www.tandfonline.com/doi/full/10.1080/08912963.2026.2614968
Caimaninae is one of the main clades within alligatoroid crocodylians. Its extant diversity encompasses six species in three genera – Caiman, Melanosuchus and Paleosuchus – and is largely native to South America; the fossil record, in contrast, reveals a far greater diversity, extending from the Late Cretaceous and, although concentrated in South America, also showing notable fossils from Central America, North America and the Caribbean. Systematic and taxonomic research on Caimaninae began in the 18th century, with phylogenetic-based systematics, taxonomy and nomenclature being applied since the 1980s. Following the publication of the International Code of Phylogenetic Nomenclature (PhyloCode), a cojoined effort by Caimaninae systematists to standardise the phylogenetic systematics and nomenclature of the group was required, which is the objective of this paper. Herein, we provide phylogenetic definitions for seven clade names: Caimaninae, Bottosauria (new clade name), Caimanini (new clade name), Jacarea, Purussauria (new clade name), Purussauridae (new clade name) and Nettosuchidae. Detailed information on each clade is provided, including taxonomic and evolutionary history, composition, fossil record, divergence dates, characteristics and previous phylogenetic studies. Our intention with this effort is to provide a stable framework on which to base further research on the diversity of the group at several levels, and to encourage the use of phylogenetic nomenclature in Crocodylia.
=====
Free pdf:
Magnus Wolf, Axel Janke & Krister T. Smith (2026)
The genome of the relict earless monitor lizard, Lanthanotus borneensis, and the Toxicofera hypothesis
BMC Biology 24: 58
doi: https://doi.org/10.1186/s12915-026-02552-4
https://link.springer.com/article/10.1186/s12915-026-02552-4
Background
The earless monitor lizard, Lanthanotus borneensis, is a unique living fossil restricted to the island of Borneo and a possible key to understanding the evolution of the venom delivery system and secondary adaptation to water in lizards and snakes (Squamata).
Results
We sequenced and de novo assembled the genome of L. borneensis to a total size of 1.5 Gbp, 975 contigs with an N50 of 52 Mbp and an L50 of 9. The genome completeness is estimated to be 93% based on the Sauropsida OrthoDB core gene set. A genome-wide set of Lepidosauria orthologs was compiled to reconstruct and date their phylogeny, resulting in 966 protein-coding sequences amounting to a concatenated alignment of 356 kbp with 188 kbp parsimony-informative sites. Based on this phylogenomic analysis, one of the largest of its kind yet conducted for Squamata, we identified that a Toxicofera clade (comprising Serpentes, Anguimorpha, and Iguania) is supported by a plurality of gene trees, but critically, support for relationships within Toxicofera is almost equally distributed amongst the three possible topologies. Our tree-dating confirms a rapid divergence of all major squamate clades within the first 10% of squamate history, which may have contributed to rampant incomplete lineage sorting. While we did not identify positive selection on genes associated with venom components at the base of Toxicofera, our analyses found strong positive selection on the giant protein titin throughout the main clades of Toxicofera and especially in snakes. Genome-wide heterozygosity is low (HO = 0.0004), as is the effective population size towards the present.
Conclusions
Future studies of the evolution of the venom delivery system in Toxicofera require a “true” species tree but also individual gene trees due to incomplete lineage sorting and the concomitant potential for hemiplasy. Titin—a key component of striated muscle elasticity—emerges as a target for future evolutionary studies in Toxicofera and especially in wide-gaped snakes (“Macrostomata”). The low observed genome-wide heterozygosity and the low but stable effective population size of L. borneensis during the large-scale habitat fluctuations on Sundaland in the Quaternary suggest an unexpected resilience to environmental perturbations but also a potentially lowered adaptive potential of this isolated lineage.
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