[Paleontology • 2026] Patagoniaemys aeschyli • A New meiolaniform Turtle from the Maastrichtian of Northern Patagonia, Argentina

Patagoniaemys aeschyli

Agnolin, Rolando, Sterli, Chimento, Novas & Muñoz, 2026

DOI: doi.org/10.4202/app.01268.2025 

 www.macnconicet.gob.ar 

Meiolaniformes are a group of chelonians including the famous horned-turtles Niolamia argentina (Patagonia) and Meiolania platyceps (Australia). In South America, the Late Cretaceous meiolaniforms are represented by two named taxa: Patagoniaemys gasparinae coming from Campanian–Maastrichtian beds of the La Colonia Formation, Chubut province, and Trapalcochelys sulcata from the Campanian–Maastrichtian beds of the Allen Formation, Río Negro Province. The aim of the present contribution is to describe a new meiolaniform chelonian coming from the Upper Cretaceous (Maastrichtian) Los Alamitos Formation, at Río Negro Province, Argentina. The material is represented by a partial basicranium, incomplete carapace and fragmentary postcranial bones (MPMIK 1839/P/33) belonging to a new species Patagoniaemys aeschyli. To this new species we refer all the material previously referred as indeterminate meiolaniid, meiolaniform and cf. Niolamia sp., coming from the same site and locality, and described by different authors since the 1980s. This new species differs from the type species P. gasparinae, particularly by the presence of longitudinal ridges in the nuchal bone. We also include brief comments about meiolaniform palaeobiogeography and the impact of K/Pg extinction event in Patagonian chelonians.

Key words: Testudinata, Meiolaniformes, Los Alamitos Formation, Maastrichtian, Cretaceous, Patagonia, Argentina.

Meiolaniform turtle Patagoniaemys aeschyli sp. nov. holotype (MPMIK 1839/P/33); Cerro Cuadrado locality, Argentina, Los Alamitos Formation Maastrichtian (Upper Cretaceous).
A. Carapace; anterior border in dorsal (A1, A2) and ventral (A3, A4) views, detail of the anterior margin in ventral view (A7, A8), showing the presence of longitudinal ridges that characterize the new species (light grey, nuchal bone; dark grey, broken surfaces).
B. Left hyoplastron fragment Scale bars 100 mm.

Testudinata Klein, 1760 

Meiolaniformes Sterli & de la Fuente, 2013 

Genus Patagoniaemys Sterli & de la Fuente, 2011a 

Type species: Patagoniaemys gasparinae Sterli & de la Fuente, 2011a;
Chubut Province, Argentina, Campanian–Maastrichtian. 

Patagoniaemys aeschyli sp. nov.

Diagnosis.—Large chelonian (maximum anterior carapace width about 60 cm, maximum inferred carapace length 80 cm). Referable to meiolaniforms by several features, namely the presence of small pits and grooves ornamenting carapace bones, anteriorly curved grooves among marginal scutes, opisthocoelous caudal vertebrae, and carapace-plastron connection through ligaments (Gaffney 1996; Hirayama et al. 2000; Sterli and de la Fuente 2013; Sterli et al. 2013). It is referred to Patagoniaemys by having a basioccipital with well-developed basal tubera with a concave surface between them, posteriorly flat occipital condyle, a shallowly notched anterior carapace margin, presence of a thickened bump on ...

Etymology: In reference to Aeschylus (525–455 BC), an ancient Greek writer often described as the father of tragedy. During a visit to the city of Gela (Italy), he was killed outside the city by a tortoise dropped by an eagle, which had mistaken his bald head for a rock suitable for shattering the shell.

the excavation work at the Los Alamitos Formation southwest of Cerro Cuadrado.  

Federico L. Agnolin, Mauro Aranciaga Rolando, Juliana Sterli, Nicolás R. Chimento, Fernando E. Novas, and Gonzalo L. Muñoz. 2026. A New meiolaniform Turtle from the Maastrichtian of Northern Patagonia, Argentina. Acta Palaeontologica Polonica. 71(1); 173-184. DOI: doi.org/10.4202/app.01268.2025 

 Researchgate.net/publication/403290389_A_new_meiolaniform_turtle_from_the_Maastrichtian_of_Northern_Patagonia_Argentina

DESCUBREN UNA TORTUGA GIGANTE DEL FIN DE LA ERA DE LOS DINOSAURIOS EN PATAGONIA

https://www.macnconicet.gob.ar/descubren-una-tortuga-gigante-del-fin-de-la-era-de-los-dinosaurios-en-patagonia

[Paleontology • 2026] Kank australis • New unenlagiid (Theropoda: Unenlagiidae) from the Chorrillo Formation (Late Cretaceous, Maastrichtian), SW Patagonia, Argentina

 

Kank australis

Motta, Rolando, Rozadilla, Agnolín, Egli, Herrera, Chimento, Coco, Tsuihiji, Manabe, Pol & Novas, 2026

 

DOI: doi.org/10.1080/02724634.2026.2656456 

A reconstruction by Gabriel Díaz Yantén

 

ABSTRACT

Unenlagiids constitute a group of paravian theropods up to now represented in Gondwanan landmasses. They are particularly diverse in northern Patagonia, where at least seven species were discovered in Upper Cretaceous beds. In southern Patagonia, by contrast, the record is restricted to a few isolated remains of indeterminate taxa from Argentina and Chile. The aim of the present contribution is to describe an unenlagiid, Kank australis gen. et sp. nov. from the Maastrichtian beds of southern Santa Cruz, southern Patagonia, Argentina. Kank australis is represented by vertebrae, isolated pedal phalanges, and shed teeth. The holotype individual has a unique combination of characters, including a highly pneumatized cervical vertebra with well-developed parapophysis and carotid processes. Further, a pedal phalanx II-2 resembles those of troodontids due the reduction of the distal condyles, and differs from other known unenlagiids. The apomorphic condition of the few available elements suggests that Kank australis was probably distinct from its kin and reinforces the hypothesis that Unenlagiidae was a morphologically disparate clade.

SYSTEMATIC PALEONTOLOGY

DINOSAURIA OWEN, 1842

SAURICHIA SEELEY, 1888

THEROPODA MARSH, 1881

PARAVES SERENO, 1997

UNENLAGIIDAE (Bonaparte, 1999)

KANK AUSTRALIS gen. et sp. nov.

Diagnosis—Medium-sized unenlagiid (phalanges similar in size to Neuquenraptor argentinus estimated in ∼27 kg; Motta, 2023) showing the following combination of characters (autapomorphies marked by an asterisk): (1) dentary teeth having mesial carinae restricted to the apical third of the crown (shared with Austroraptor); (2) labiolingually compressed maxillary teeth “8” in cross-section (shared with Buitreraptor); (3) dentary teeth having a crenulate mesial carina restricted to its apical third; (4) cervicodorsal vertebra having three pneumatic foramina on its ventral surface*; (5) cervicodorsal vertebra having epipophyseal fossa*; and (6) phalanx 2-II showing reduced distal condyles and collateral pits located very close to the anterodorsal corner of the condyles (shared with troodontids).

Etymology—“Kank,” in reference to the “elder Rhea,” who created the constellation Choiols (Southern Cross constellation) in the Aonikenk mythology, and “australis,” which means “from south” in Latin, in reference to the southern latitude where this dinosaur was found.

 

Matías J. Motta, Alexis M. Aranciaga Rolando, Sebastián Rozadilla, Federico L. Agnolín, Federico Brissón Egli, Gerardo P. Álvarez Herrera, Nicolás R. Chimento, Gastón Lo Coco, Takanobu Tsuihiji, Makoto Manabe, Diego Pol and Fernando E. Novas. 2026. New unenlagiid from the Chorrillo Formation (Late Cretaceous, Maastrichtian), SW Patagonia, Argentina. Journal of Vertebrate Paleontology. e2656456. DOI: doi.org/10.1080/02724634.2026.2656456  [28 May 2026]

https://newsroom.taylorandfrancisgroup.com/heron-like-fish-eating-dinosaur-from-70-million-years-ago-discovered-in-argentina

https://www.macnconicet.gob.ar/kank-australis-el-nuevo-raptor-descubierto-en-la-patagonia-argentina

[Paleontology • 2026] Alnashetri cerropoliciensis • Argentine Fossil rewrites Evolutionary History of a baffling Dinosaur Clade

Alnashetri cerropoliciensis Makovicky, Apesteguía & Gianechini, 2012

in Makovicky, Mitchell, Meso, Gianechini, Cerda et Apesteguía, 2026.  

 DOI: doi.org/10.1038/s41586-026-10194-3

Abstract

Alvarezsauroids are an enigmatic clade of predominantly small-bodied theropod dinosaurs that are known mainly from the Jurassic to Cretaceous periods of Asia and South America. Late Cretaceous alvarezsauroids possess specialized forelimbs adapted for digging, minute supernumerary teeth and heightened sensory capacities, and are interpreted as myrmecophagous. They are hypothesized to exhibit evolutionary miniaturization coupled to their dietary specialization. Fragmentary South American taxa are traditionally arrayed as a paraphyletic grade with respect to the Late Cretaceous Asian subclade Parvicursorinae, invoking dispersal to explain their disjunct distributions. Here we describe a skeleton of the alvarezsauroid Alnashetri cerropoliciensis representing to our knowledge the most complete and smallest South American taxon to date. We also recognize two alvarezsauroids among historic taxa from the Northern Hemisphere. Phylogenetic analysis recovers Alnashetri among basal non-alvarezsaurids, rendering South American taxa polyphyletic. Combined with the new taxa recognized here, our biogeographical analyses infer a Pangaean ancestral distribution for Alvarezsauroidea, with vicariance dominating the early history of the clade. The early branching position of Alnashetri among larger-bodied relatives revises best-fit models of body size evolution in alvarezsauroids—we find no support for evolutionary miniaturization but, rather, find support for repeated evolution within a narrow body size range.

 

Peter J. Makovicky, Jonathan S. Mitchell, Jorge G. Meso, Federico A. Gianechini, Ignacio Cerda and Sebastian Apesteguía. 2026. Argentine Fossil rewrites Evolutionary History of a baffling Dinosaur Clade.  Nature. DOI: doi.org/10.1038/s41586-026-10194-3 [25 February 2026]

 x.com/NatureJapan/status/2031626177027387582

[Herpetology • 2026] Philodryas pseudomamba • Morphological and Molecular Variation reveal Cryptic Diversity in the Racer Philodryas patagoniensis (Girard, 1858) (Squamata: Colubridae)

[B, E, H] Philodryas patagoniensis (Girard, 1858); 

[C, F, I] Philodryas pseudomamba Pietro, Sánchez, Poljak & Alcalde, 2026 

 

DOI: doi.org/10.3897/vz.76.e169219

Abstract

We analysed the genetic and morphological variation in Philodryas patagoniensis, a widely distributed South American racer snake. Two well-differentiated haplogroups were identified using mitochondrial gene sequences (12S and 16S) and the nuclear gene c-mos. Genetic divergence between these haplogroups correlates strongly with morphological differences, allowing the recognition of two morphotypes within P. patagoniensis. We integrated genetic and morphological data into a total evidence analysis using parsimony. Our results support the distinction between the two haplogroups/morphotypes, consistent with recognising two species within P. patagoniensis. Accordingly, we re-describe P. patagoniensis, refining its morphological variation and geographical distribution to reflect the observed genetic differentiation, and describe a new species. Morphological characteristics can distinguish the two species, including body measurements, scale patterns, and cranial osteology. The new species differs from P. patagoniensis sensu stricto in traits associated with arboreal habits, which are strongly correlated with the distribution of the two taxa across forested and open habitats in South America. Furthermore, P. patagoniensis sensu stricto has a significant Lycosa spider component in its diet, which is absent in the newly described species.

Keywords: Biodiversity, Dipsadinae, Philodryadini, Serpentes, South America, systematics, taxonomy

In-life colouration of
A a Monte of Plains and Plateaus specimen of P. patagoniensis (Rio Negro, Chipauquil, Meseta de Somuncura),
B a Pampa specimen of  P. patagoniensis (Buenos Aires, Sierra de Curamalal), and
C a Humid Chaco specimen of P. pseudomamba sp. nov. (Chaco, Tres Isletas).

Photos are not to scale. Photo credits: David Vera (A), Eduardo Schaeffer (B).

Lateral (A–C), dorsal (D–F), and ventral (G–I) views of the heads of representative specimens from both morphotypes.
The left column (A, D, G) shows a B-morphotype specimen from the Monte of Plains and Plateaus (Rio Negro province, MLP.R 5313). The middle column (B, E, H) features a B-morphotype specimen from the Pampa (Buenos Aires province, MLP.R 6039). The right column (C, F, I) presents an A-morphotype specimen from the Humid Chaco (Corrientes province, MLP.R 5449, holotype). Arrows and asterisks highlight character states (see File S2). Photographs A–F include a line-drawing diagram highlighting in grey the scales involved in each character state, as indicated by arrows and asterisks in the corresponding images. Scale bars = 5 mm.

Philodryas pseudomamba sp. nov.

Diagnosis. Philodryas pseudomamba sp. nov. differs from all other species of the genus by the following combination of characters: (1) dorsal scale rows 19–19–15, (2) HL/TTL between 2 and 3.4%, (3) SVL/TTL between 68 and 77.7%, (4) TL/TTL between 22.2 and 32%, (5) ventral scales between 166 and 199, (6) subcaudal scales between 81 and 124, (7) loreal scale rectangular, longer than tall, (8) dorsal half of the preocular markedly exceeding the posterior margin of the loreal, (9) supralabials 7 (3,4), (10) lateral border of the supraocular straight in dorsal view, (11) first temporal scale large (height being less than 40% of the length), (12) dorsal scales of the head with completely immaculate olive colouration featuring tiny black scale margins, (13) dorsal body design dotted, not maculated, and (14) ventral scales lacking lateral black spots.

Etymology. The prefix pseudo of the epithet derives from Greek, meaning “falseness” or “falsehood”. Mamba refers to the term “imamba” used in the Bantú language (spoken by various African ethnic groups) to designate snakes of the genus Dendroaspis, commonly known in English and other languages as “mambas”. The species name was explicitly inspired by D. polylepis (the black mamba), due to the general physical resemblance and notably aggressive behaviour shared by both species.

 Diego Omar Di Pietro, Julieta Sánchez, Sebastián Poljak and Leandro Alcalde. 2026. Morphological and Molecular Variation reveal Cryptic Diversity in the Racer Philodryas patagoniensis (Girard, 1858) (Squamata: Colubridae). Vertebrate Zoology. 76: 93-119. doi.org/10.3897/vz.76.e169219 [10 Feb 2026]

[PaleoMammalogy • 2026] Notopolytheles joelis • First unambiguous evidence of Multituberculata from the Late Cretaceous of South America

 

upper left: upper molar Notopolytheles joelis in occlusal view.

lower left: plagiaulacoid tooth of Argentodites coloniensis.

Notopolytheles joelis

Gelfo, Goin & Vega, 2025

  DOI: doi.org/10.1038/s41598-025-25255-2

Abstract

We report a left upper first molar of a multituberculate mammal, from the Upper Cretaceous La Colonia Formation, Chubut Province, Argentina, which is here assigned to Notopolytheles joelis gen. et sp. nov. (Cimolodonta,?Neoplagiaulacidae). Multituberculates have been previously reported from Gondwanan land masses, but to date, only records from Australia, Madagascar, and India have been taxonomically undisputed. In South America, all previous assignments were debated or later referred to Gondwanatheria. These records include isolated molars attributed to Ferugliotheriidae and Argentodites coloniensis, only known from a plagiaulacoid premolar and originally assigned to the ?Cimolodonta. Since no molar with definitive multituberculate features could ever be found in the Upper Cretaceous of Patagonia, A. coloniensis was considered a junior synonym of the ferugliotheriid Ferugliotherium windhauseni. Notopolytheles joelis gen. et sp. nov. displays a typical multituberculate molar configuration of three rows of tetrahedral cups, with a cusp formula of 7B:8M:4L similar to Neoplagiaulacidae. The lower position of the buccal cusp row supported by a single large labial root suggest a high level of endemism. This finding provides strong and renewed support for the hypothesis that ferugliotheriids lack a plagiaulacoid p4 and that Argentodites coloniensis is indeed a multituberculate.

Keywords: South America, Patagonia, La Colonia Formation, Late Cretaceous, Multituberculata, Gondwanatheria

Left: upper molar of the new species Notopolytheles joelis in occlusal view.
Right: plagiaulacoid tooth of Argentodites coloniensis.

Scale bar = 1 mm.

Reconstruction of the small multituberculate Notopolytheles joelis from the Late Cretaceous La Colonia Formation, Chubut Province, Argentina. (by Manuel Copello)

Mammalia Linnaeus, 1758.

Multituberculata Cope, 1884.

Cimolodonta McKenna, 1975.

?Neoplagiaulacidae Ameghino, 1890.

Notopolytheles joelis gen. and sp. nov.

Etymology: The genus name refers to ‘southern multituberculate’ and derives from three Greek roots: noto- (south), poly- (many), and theles (protuberance), the last two in reference to the multiple cusps characteristic of multituberculate teeth. The specific epithet joelis is named after Joel Hernán Carino, who discovered the tooth.

Javier N. Gelfo, Francisco J. Goin  and Nahuel A. Vega. 2025. First unambiguous evidence of Multituberculata from the Late Cretaceous of South America. Scientific Reports. 15, 41500. DOI: doi.org/10.1038/s41598-025-25255-2 [24 November 2025]

 

A TINY FOSSIL TOOTH REWRITES THE HISTORY OF SOUTHERN MAMMALS

https://go.nature.com/4rnCGwU

 

[Paleontology • 2026] Yeneen houssayi gen. et sp. nov. and An overview of the Sauropod titanosaurian Diversity from Cerro Overo – La Invernada Area (Bajo de la Carpa Formation, Santonian)

Yeneen houssayi 

Filippi, Bellardini, Carballido, Méndez & Garrido, 2026

DOI: doi.org/10.1080/08912963.2025.2584707 

Illustration: Gabriel Lío

ABSTRACT

The fossil record of titanosaur sauropods for the Upper Cretaceous of the Neuquén Basin is remarkably extensive. However, for the Bajo de la Carpa Formation (Santonian) only five nominate species are recorded (Rinconsaurus caudamirus, Bonitasaura salgadoi, Traukutitan eocaudata, Overosaurus paradasorum, and Inawentu oslatus), the latter two coming from the Cerro Overo-La Invernada (CO-LI) area. Here we present a new titanosaur sauropod from La Invernada, Yeneen houssayi gen. et sp. nov. (MAU-Pv-LI-538). The new species is characterised by a series of distinctive features in dorsal, sacral and caudal vertebrae. Phylogenetic analysis indicates that Yeneen is closely related to Narambuenatitan and Overosaurus, as a basal member of an unnominated clade (called ‘Clade A’) of derived non-lithostrotian saltasauroids. The evidence provided by the Cerro Overo – La Invernada sauropod titanosaur fauna suggests that, during the Santonian, species diversity was relatively high and that at least two lineages coexisted: Collossosauria and Saltasauroidea. This finding makes the CO-LI area the one with the greatest diversity of titanosaurs for the Santonian of the Neuquén basin (as it is also for abelisaurid theropods), which makes it an exceptional area to understand the evolution of dinosaur faunas for this period.

KEYWORDS: Titanosauria, diversity, upper Cretaceous, Neuquen Basin, Gondwana

Systematic Paleontology

Dinosauria Owen, 1842

Saurischia Seeley, 1888

Sauropoda Marsh, 1878

Titanosauriformes Salgado, Coria and Calvo, Citation1997

Somphospondyli Wilson and Sereno, 1998

Titanosauria Bonaparte and Coria, Citation1993

Yeneen houssayi gen. et sp. nov.

Derivation name: Yeneen, is known in the Tehuelche (Aonikenk) Culture as a spirit or entity related to winter, cold and winter nature in general, alluding to the La Invernada, a Spanish word that refers to the site where the cattle spend the winter. The specific epithet, houssayi, is in honour of Dr. Bernardo Alberto Houssay, Nobel Laureate in Medicine and member of the commission that promoted the creation of CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina).

L. S. Filippi, F. Bellardini, J. l. Carballido, A. H. Méndez and A. C. Garrido. 2026. Yeneen houssayi gen. et sp. nov. and An overview of the Sauropod titanosaurian Diversity from Cerro Overo – La Invernada area (Bajo de la Carpa Formation, Santonian), North Patagonia, Argentina. Historical Biology: An International Journal of Paleobiology. DOI: doi.org/10.1080/08912963.2025.2584707 [12 Jan 2026]

[Paleontology • 2025] Helianthochelys redondita • the southernmost dermochelyid turtle from the Miocene

Helianthochelys redondita 

Sterli, Vlachos, Cuitiño, Cerda & Buono, 2025

 ameghiniana.org.ar 

mef.org.ar

Abstract

 Dermochelyids are a unique lineage of turtles where the primary carapace underwent an extreme reduction, with its maximum expression in the extant Dermochelys coriacea. Above the primary carapace (thecal), a secondary (epithecal) carapace formed by thousands of ossicles appeared in the late Paleocene. In general, the fossil record of dermochelyids is incomplete, fragmentary, and patchy. Besides, no indepth and detailed studies on their anatomy led to a poorly resolved alpha taxonomy. In this contribution, we present one of the most complete dermochelyids in the world. Our new turtle was found in the Gaiman Formation (Lower Miocene) in Chubut, Argentina. This Burdigalian record of Patagonia represents the southernmost species in the fossil record of dermochelyid turtles in the Southern Hemisphere in the Miocene. The histological analysis of long bones shows a highly remodeled cortex, a unique condition in turtles. The tissue compaction recorded in this new turtle would suggest it was a very old individual. The phylogenetic analysis recovered the new species in a clade characterized by longitudinal ridges in the carapace and ossicles arranged in a “sunflower” pattern. Exploring the diversity patterns of dermochelyids, we recognize two peaks of diversity and three extinction events, comparable with those observed in other marine tetrapods (e.g., cetaceans, penguins). 

Key words. Dermochelyidae. Marine tetrapods. Gaiman Formation. Patagonia. Diversity.

Anatomy of Helianthochelys redondita gen. and sp. nov. MPEF-PV 10918 from the Gaiman Formation of Chubut Province, Argentina.
1, dorsal view of the carapace with a reconstruction of the carapace outline. 2, oblique view of the carapace showing the primary, middle, secondary, and tertiary ridges. 3, detail of the carapace showing the sunflower pattern and defining the disc and ray ossicles; white scale bar equals 10 cm. 4, visceral view of the carapace showing the various bones in their recovery position. Black scale bar equals 50 cm.

  Testudinata Klein, 1760 (sensu Joyce et al., 2020a) 

Testudines Batsch, 1788 (sensu Joyce et al., 2020b) 

Cryptodira Cope, 1868 (sensu Joyce et al., 2020c) 

Durocryptodira Danilov & Parham, 2006 (sensu Joyce et al., 2021) 

Americhelydia Joyce et al., 2013 (sensu Joyce et al., 2021) 

Chelonioidea Baur, 1893 (sensu Joyce et al., 2021) 

Dermochelyidae Lydekker, 1889 (sensu Joyce et al., 2021) 

Helianthochelys redondita gen. et sp. nov.  

Derivation of the name. The generic name, Helianthochelys, comes from the combination of the Greek words ήλιος (Helios, sun) and ανθός (anthos, flower) combined as “sunflower” and the feminine word χέλυς (chelys, turtle), in allusion to the sunflower pattern of ossicles in the secondary carapace. The specific name, redondita, refers to the type locality Estancia La Redonda Chica, hence the Latin diminutive -ita in the end. 

Holotype. MPEF-PV 10918, almost complete carapace (secondary ossicles and nuchal bone) with a putative skull fragment (jugal) and postcranial elements (cervical vertebrae 4, 7, and 8, ten thoracic vertebrae, thoracic ribs, two sacral neural arches, three caudal vertebrae, both scapulae, both pubes, both ischia, both ilia, right femur), forming part of the paleoherpetological collection of MPEF (see Sterli et al., 2021 for additional information). 

Type locality. Coastal creek located 5 km east of La Redonda Chica House in La Redonda Chica Farm, Chubut province, Argentina (Fig. 2). Age. Gaiman Formation, Burdigalian, Early Miocene (Cuitiño et al., 2023). 

Diagnosis (same for genus and species). Helianthochelys redondita is a dermochelyid turtle, based on the presence of a mosaic carapace (psephophore dermochelyid turtles) and the remaining diagnostic synapomorphies listed above. Helianthochelys redondita shares with other more crownward dermochelyids the presence of the characteristic sunflower pattern formed by the ossicles (helianthophore dermochelyid turtles). Differs from Natemys and is associated with more derived helianthophores in the absence of some elongated ossicles and the presence of anteroposterior ridges. Differs from the type of Psephophorus polygonous and is associated with other closely related taxa from the Atlantic coasts (e.g., “Psephophorus” scaldii and Westerschelde specimen from Europe and “Psephophorus” calvertensis from the Atlantic side of North America) due to the absence of change of curvature until the tip of the ridge, in cross-section. Differs from all these Atlantic helianthophores based on the presence of secondary (and even tertiary) anteroposterior ridges between the five primary ridges. Differs from the Westerschelde specimen and “Psephophorus” calvertensis and is more closely related to “Psephophorus” scaldii based on higher counts of “ray” ossicles around the central “disk” ossicle (up to 13 ossicles) and the presence of comparatively thinner, medium-thick (0.6–1.1 cm) ossicles as well. Differs from “Psephophorus” scaldii based on the disk/ray pattern: Helianthochelys redondita has usually three ray ossicles between two successive disk ossicles, whereas “Psephophorus” scaldii has, usually, a single ray ossicle between two successive disk ossicles.  

 

 

Juliana Sterli, Evangelos Vlachos, José Ignacio Cuitiño, Ignacio A. Cerda, and Mónica Romina Buono. 2025. SOUTHERNMOST DERMOCHELYID TURTLE FROM THE MIOCENE. AMEGHINIANA. 62(4); 1–19. https://www.ameghiniana.org.ar 

https://www.ameghiniana.org.ar/index.php/ameghiniana/libraryFiles/downloadPublic/149

https://mef.org.ar/blog/2025/10/03/nueva-especie-de-tortuga-marina-gigante-de-20-millones-de-anos-hallada-en-patagonia/

https://x.com/mefpatagonia/status/1974240673780916342

[Paleontology • 2025] Joaquinraptor casali • Latest Cretaceous megaraptorid theropod Dinosaur sheds light on megaraptoran evolution and palaeobiology

 

Joaquinraptor casali 

Ibiricu, Lamanna, Alvarez, Cerda, Caglianone, Cardozo, Luna & Martínez, 2025 

 DOI: doi.org/10.1038/s41467-025-63793-5 

Artwork by  Andrew McAfee

Abstract

Recent fossil discoveries have cast considerable light on the palaeobiology of Megaraptora, a group of large-clawed carnivorous theropod dinosaurs known from Cretaceous deposits in Asia, Australia, and especially South America. Nevertheless, many important aspects of megaraptoran morphology and evolution remain poorly understood, due in large part to the fragmentary nature of most fossils of these theropods and the scarcity of anatomically overlapping skeletal elements among the known taxa. Here we report a previously unknown megaraptoran genus and species represented by a partially articulated partial skeleton recovered from an uppermost Cretaceous stratum of the Lago Colhué Huapi Formation of south-central Chubut Province in central Patagonia, Argentina. Pertaining to the derived megaraptoran subclade Megaraptoridae, the taxon is among the most completely represented and latest-surviving megaraptorans. Its stratigraphic occurrence indicates that these dinosaurs likely persisted to the Cretaceous/Palaeogene boundary; moreover, the preservation of a crocodyliform humerus between the dentaries of the new theropod may provide information on megaraptoran dietary preferences and feeding strategies. Megaraptorids appear to have been the apex predators in central and southern Patagonian palaeoecosystems approaching the end of the Cretaceous, in contrast to more northerly areas of South America where these niches were occupied by other non-avian theropod groups.

 Osteology of Joaquinraptor casali gen. et sp. nov.
a Skeletal reconstruction of Joaquinraptor in left lateral view with preserved elements in blue (some reversed from right side) (modified and updated from Lamanna et al.7 [these authors’ Fig. 1e], which was in turn modified by A. McAfee from an original illustration by T.K. Robinson). Right maxilla in lateral (b) and medial (c) views. Skull roof, braincase, and atlantal intercentrum in dorsal (d) and ventral (e) views. f Probable right postorbital in lateral view. g Right quadrate in anterior view. Right and left dentaries in lateral and medial views (right dentary in lateral view and left dentary in medial view in h; opposite in i). j Two articulated middle or posterior caudal vertebrae in right lateral view. k Dorsal rib in anterior view. l Anterior haemal arch in anterior view. m Left scapulocoracoid in lateral view. Left humerus in anterolateral (n), lateral (o), and medial (p) views. Left radius in anterior (q) and lateral (r) views. Left ulna in lateral (s) and posterior (t) views. u Right manual ungual II (=manual phalanx II-3) in lateral view. Left femur in anterior (v) and posterior (w) views. x Distal right tibia in anterior view. y Right pedal ungual III (=pedal phalanx III-4) in medial view. Dashed lines indicate missing areas of scapulocoracoid and femur.

Systematic palaeontology

Saurischia Seeley, 1887 

Theropoda Marsh, 1881 

Tetanurae Gauthier, 1986 

Megaraptora Benson, Carrano, and Brusatte, 2010 

Megaraptoridae Novas, Agnolín, Ezcurra, Porfiri, and Canale, 2013 

Joaquinraptor casali gen. et sp. nov.

Etymology: Joaquín, in tribute to the son of the first author (L.M.I.) and the informal name given to the locality when the skeleton of the taxon was discovered (Valle Joaquín); Latin, raptor, thief. Specific epithet casali in recognition of Dr. Gabriel Andrés Casal for his many contributions to knowledge of the Cretaceous palaeontology and geology of central Patagonia (including the formal recognition and naming of the formation from which this megaraptorid was recovered).

Joaquinraptor casali with an ancient crocodile relative's front leg in its mouth.

Artwork by  Andrew McAfee

 

Lucio M. Ibiricu, Matthew C. Lamanna, Bruno N. Alvarez, Ignacio A. Cerda, Julieta L. Caglianone, Noelia V. Cardozo, Marcelo Luna and Rubén D. Martínez. 2025. Latest Cretaceous megaraptorid theropod Dinosaur sheds light on megaraptoran evolution and palaeobiology. Nature Communications. 16: 8298. DOI: doi.org/10.1038/s41467-025-63793-5 [23 September 2025]

[Diplopoda • 2025] Pleonaraius spelaeus • Into the Depths of Patagonia: The First Troglobitic Species of Pleonaraius Attems, 1898 (Polydesmida: Dalodesmidae) from Argentina

Pleonaraius spelaeus 

Romero-Rincon & Ferreira, 2025

 DOI: doi.org/10.3390/arthropoda3030013 

 Researchgate.net/publication/395231965

Abstract

A new troglobitic species of Dalodesmidae, Pleonaraius spelaeus n. sp., is described from Rolo Vergara Cave, Neuquén Province, Argentina. This species represents the fourth known troglobitic member of the family, the first troglobitic species of Dalodesmidae recorded in South America, and the first known troglobitic millipede from Argentina. Pleonaraius spelaeus n. sp. is distinguished from its congeners by the absence of cuticular pigmentation and a unique combination of gonopodal characters. Ecological notes, a key, and a distribution map of Pleonaraius species are also provided.

Keywords: cave; Diplopoda; key; new species; taxonomy

 (A) Aereal view of the area where the cave in which Pleonaraius spelaeus n. sp. was found (yellow arrow indicates the cave entrance); (B) cave entrance at the bottom of the sinkhole; (C) cave conduct where the specimens were found and collected; (D) living male.

Pleonaraius spelaeus n. sp.

Diagnosis. Based on the gonopodal conformation, the new species differs from its congeners by the following combination of characters: mb simple (vs. bifurcated and complex in P. omalonotus) and directed ventrad at its apex (vs. directed laterad in P. pachyskeles and P. omalonotus). lb simple with apex acuminate (vs. apex suberect in P. pachyskeles). Presence of pr as in P. pachyskeles (vs. absence in P. omalonotus).

Etymology. Spelaeus, adjective in the masculine gender. The epithet as a reference to the Latin word spelaeus, meaning “cave”.

Distribution. Only known from in Rolo Vergara Cave, municipality of Chos Malal, Neuquén Province, Argentina (Figure 5).

  Juan Romero-Rincon and Rodrigo Lopes Ferreira. 2025. Into the Depths of Patagonia: The First Troglobitic Species of Pleonaraius Attems, 1898 (Polydesmida, Dalodesmidae) from Argentina. Arthropoda. 3(3), 13. DOI: doi.org/10.3390/arthropoda3030013 [3 September 2025] 

 Researchgate.net/publication/395231965_The_First_Troglobitic_Pleonaraius_from_Argentina

[Paleontology • 2025] Kostensuchus atrox • A New large hypercarnivorous Crocodyliform (Mesoeucrocodylia: Peirosauridae) from the Maastrichtian of Southern Patagonia, Argentina

 

Kostensuchus atrox

Novas, Pol, Agnolín, Carvalho, Manabe, Tsuihiji, Rozadilla, Lio & Isasi, 2025

  

DOI: doi.org/10.1371/journal.pone.0328561

Abstract

The first crocodyliform specimen from the Maastrichtian Chorrillo Formation (Austral Basin, Patagonia) is here described. The discovery was made about 30 km to the SW of the town of El Calafate (Province of Santa Cruz, Argentina) and consists of a beautifully preserved and articulated skull and jaws, and part of the postcranial skeleton that were preserved encased in a large concretion. This new taxon belongs to the notosuchian clade Peirosauridae, representing the latest and southernmost record for this group of crocodyliforms. The new taxon is recovered as closely related to other robust and broad-snouted peirosaurids that lived by the end of the Cretaceous Period, such as Colhuehuapisuchus from the Maastrichtian of Central Patagonia and Miadanasuchus oblita from the Maastrichtian of Madagascar. The completeness of the new specimen reveals, for the first time, the anatomy and body plan of a large and broad snouted peirosaurid. The new taxon bears large ziphodont teeth, a broad oreinirostral snout that is only slightly longer than 50% the skull length, and a deep adductor chamber in the temporal region and posterior mandibular ramus. The anterior region of its postcranial skeleton is preserved and shows broad scapula and a robust humerus features previously known in large predatorial notosuchians. The new crocodyliform adds to the predatorial component of terrestrial ecosystems at high paleolatitudes by the end of the Cretaceous Period.

Systematic paleontology

Crocodyliformes Hay, 1930

Mesoeucrocodylia Whetstone and Whybrow, 1980

Peirosauria Leardi et al., 2024

Peirosauridae Gasparini, 1982

Kostensuchus atrox gen. et sp. nov.

Etymology. Kosten, refers to the Patagonian wind in Aonikenk language; and suchus, latinized from the Greek Souchos in references to the Egyptian crocodile-headed god (Sebek). The species epithet atrox means harsh in Greek.

Holotype. MPM-PV 23554, articulated skull, jaws, cervical, axial skeleton remains including cervical, dorsal, and sacrals, rows of osteoderms along the vertebral sequence, cervical and dorsal ribs, scapular and pelvic girdles, complete right humerus and partial left humerus, and fragmentary remains of the hindlimbs.

Locality, horizon, and age. Lower section of the Chorrillo Formation, at Estancia La Anita, approximately 30 km SW from El Calafate city (Fig 1). The specimen comes from a concretionary level exposed at the locality “Puma cave” (locality 4, 5), approximately 60 meters from the base of the Chorrillo Formation.

Diagnosis. Kostensuchus gen. nov. is among the largest known peirosaurids (dorsal skull length = 49 cm) diagnosed by the following combination of characters (autapomorphies marked by *): skull proportionally shorter, wider and higher than in other peirosaurids (e.g., Hamadasuchus, Lomasuchus, Montealtosuchus); rostrum comprising slightly over 50% the total skull length; sinusoidal alveolar margin of maxilla (shared with Hamadasuchus); completely ossified internarial bar; lacrimal lateral surface faintly ornamented and slightly depressed between antorbital fenestra and orbit*; jugal reaching the ventral end of a circular antorbital fenestra; subtrapezoidal external supratemporal fenestra, occupying close to 70% of skull roof width; absence of anterior floor of supratemporal fossa; flat dorsal surface of parietal in occipital view; distinct step on dorsal surface of the posterolateral process of squamosal; broad palatine anterior margin, forming a bread transversal suture with maxilla; paired parasagittal ridges on the ventral surface of the basisphenoid; convex dorsal edge of surangular and craniomandibular articulation located above the level of dentary toothrow; ziphodont teeth; humerus with vertical orientation of insertion area of M. subscapularis above internal tuberosity; distal end of deltopectoral crest curves medially surpassing the lateromedial midpoint of humeral shaft; anterior surface of distal end of humerus separated from shaft by a distinct step forming a shelf.

Skull and jaw of Kostensuchus atrox gen. et sp. nov.
Photographs in (A) right lateral, (B) dorsal, and (C) ventral views. Interpretative drawings in (D) right lateral, (E) dorsal, and (F) ventral views.

 Abbreviations: ang, angular; ap, anterior palpebral; de, dentary; ec, ectopterygoid; fr, frontal; j, jugal; la, lacrimal; mx, maxilla; pa, parietal; pal, palatine; pmx, premaxilla; pnf, perinarial fossa; po, postorbital; pp, posterior palpebral; pt, pterygoid; q, quadrate; qj, quadratojugal; na, nasal; rarp, retroarticular process; sang, surangular; sof, suborbital fossa; spl, splenial; sq, squamosal; stf, subtympanic foramen. Scale bar 5 cm.

 

 Fernando E. Novas, Diego Pol, Federico L. Agnolín, Ismar de Souza Carvalho, Makoto Manabe, Takanobu Tsuihiji, Sebastián Rozadilla, Gabriel L. Lio and Marcelo P. Isasi. 2025. A New large hypercarnivorous Crocodyliform from the Maastrichtian of Southern Patagonia, Argentina. PLoS One. 20(8): e0328561.  DOI: doi.org/10.1371/journal.pone.0328561 [August 27, 2025]