[Botany • 2026] Polystemma cualense (Apocynaceae: Asclepiadoideae) • A New Species from western Mexico

Polystemma cualense  C.D.Sánchez, S.Islas & A.Black, 

in Sánchez-Sánchez, Islas-Hernández et Black, 2026. 

DOI: doi.org/10.3897/phytokeys.276.176723 

Abstract

A new species of Polystemma is described from the Sierra El Cuale, Jalisco, Mexico. Polystemma cualense is distinguished from its congeners, particularly P. horconesense, by a gynostegial corona higher than the gynostegium, longer external corona lobes, and a black gynostegium. Morphological data were obtained by examining herbarium specimens, consulting digital images from iNaturalist, and reviewing specialized literature. A preliminary conservation assessment based on IUCN criteria indicates that it is a Critically Endangered (CR) species due to its restricted area of occupancy and threats from deforestation, agriculture, and livestock grazing. The discovery of P. cualense increases the known diversity of Polystemma in Jalisco and highlights the floristic importance of the Sierra El Cuale.

Key words: Asclepiadoideae, high diversity, Jalisco, Sierra El Cuale

Polystemma cualense.
A. Complete plant; B. Inflorescence; C. Detail of gynostegium; D. Pollinarium. E. Immature follicle with sepal remnants.

Polystemma cualense C.D.Sánchez, S.Islas & A.Black, sp. nov.

  

Diagnosis. Polystemma cualense resembles P. horconesense in having flowers similar in size and shape. Polystemma cualense differs in having a gynostegial corona higher than the gynostegium (vs. gynostegial corona the same height as the gynostegium), external gynostegial corona lobes 3–4 mm length (vs. 0.5–0.6 mm length) and gynostegium black (vs. gynostegium green-yellowish).

 Cristóbal Daniel Sánchez-Sánchez, Carla Sofía Islas-Hernández and Adam W. Black. 2026. Polystemma cualense (Apocynaceae), A New Species from western Mexico. PhytoKeys. 276: 245-251. DOI: doi.org/10.3897/phytokeys.276.176723   [18 Jun 2026]

 

[Botany • 2026] Syngonium turipachense (Araceae) • A New Species of Syngonium sect. Syngonium from Chiapas, Mexico

Syngonium turipachense 

in Jiménez, Pérez-Farrera, Croat, Martínez-Martínez, Méndez, Hentrich et Aguilar-Rodríguez, 2026.

 DOI: doi.org/10.11646/phytotaxa.750.3.6 

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The genus Syngonium is represented in Mexico by ten species, seven of which are registered for the state of Chiapas. During fieldwork between 2020 and 2025 in Berriozabal, Chiapas, we discovered an undescribed species of Syngonium sect. Syngonium that is morphologically similar to S. neglectum, but differing from that species in having one or two inflorescences per axil, glaucous stems and spathe tube, a spathe blade almost twice as long as the staminate portion of the spadix, staminate flowers retuse at the apex, glaucous immature infructescence and the spathe not persistent in mature fruits.

Aroid, Berriozabal, Reserva La Pera, Syngonium angustatum, Syngonium neglectum, Monocots

Syngonium turipachense

PEDRO DÍAZ JIMÉNEZ, MIGUEL ÁNGEL PÉREZ-FARRERA, THOMAS B. CROAT, MAURICIO GERÓNIMO MARTÍNEZ-MARTÍNEZ, GASPAR MORENO MÉNDEZ, HEIKO HENTRICH, PEDRO A. AGUILAR-RODRÍGUEZ. 2026. A New Species of Syngonium sect. Syngonium (Araceae) from Chiapas, Mexico.  Phytotaxa. 750(3); 207-215. DOI: doi.org/10.11646/phytotaxa.750.3.6 [2026-04-07]

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[Botany • 2026] Dioon nuusaviorum (Zamiaceae) • A striking New Species from pine and pine-oak forest of Guerrero, Mexico

Dioon nuusaviorum Mart.-Domínguez, Nic.-Mor. & D.W.Stev.,   

in Martínez-Domínguez, Nicolalde-Morejón, Stevenson, Lorea-Hernández et Vergara-Silva, 2026.

DOI: doi.org/10.3897/phytokeys.274.173907 

Abstract

Taxonomic studies in cycad genera using multiple approaches have refined the delimitation of many species. In the case of Dioon Lindl., a Mesoamerican genus, a reliable classification has been achieved through taxonomic work carried out since the description of the genus and pioneering studies in Mexico during the 1980–90s. Here, we describe a new species from Guerrero based on evidence collected from populations encountered during fieldwork carried out in 2019. These populations had previously been considered morphologically similar to Dioon holmgrenii De Luca, Sabato & Vázq. Torres, which has a markedly disjunct distribution in Oaxaca. After studying herbarium specimens and making extensive observations on vegetative and reproductive structures from different populations in Oaxaca, we have concluded that the disjunct populations analysed in 2019 represent a distinct and new species of Dioon, separate from the two most phenotypically similar species—namely, D. stevensonii Nic.-Mor. & Vovides and D. holmgrenii. A key to geographically proximal and morphologically similar species as well as to the other species occurring in Guerrero and Oaxaca States is also presented. The proposed new species, Dioon nuusaviorum Mart.-Domínguez, Nic.-Mor. & D.W.Stev., is endemic to Guerrero and inhabits pine and pine-oak forest. Its conservation status, assessed on the based IUCN guidelines and criteria, qualifies as Endangered.

Key words: Cycadales, cycads, Mesoamerica, Neotropics, Sierra Madre del Sur

Dioon nuusaviorum sp. nov.
A. Ovulate strobilus; B. Megasporophyll; C. Basal scale of megasporophyll; D. Microsporophyll; E. Leaflets variation; F. Cataphylls; G. Seeds variation; H. New leaves; I. Leaves at emergence; J. Leaf at maturity.

Dioon nuusaviorum sp. nov., in habitat.
 A. Ovuliferous plant in habitat; B. Eumaeus sp; C. Population in La Trinidad; D. Vegetation view; E. Ovulate strobilus at maturity in habitat. 

Dioon nuusaviorum Mart.-Domínguez, Nic.-Mor. & D.W.Stev., sp. nov.

 

Diagnosis. Dioon nuusaviorum sp. nov. differs from D. holmgrenii by having leaflets imbricate to strongly imbricate, each with three to six long marginal teeth (0.26–0.37 cm long), a margin of the leaflets curved acroscopically, microsporophylls with an acuminate apex and megasporophylls with an apiculate apex. In contrast, D. holmgrenii has non-imbricate leaflets (generally a 0.2–1.0 cm between leaflets) with two to five short teeth on the distal margin (0.15–0.29 cm long), a margin of the leaflets straight, microsporophylls with an acute apex and megasporophylls with an acuminate apex. In comparison to D. stevensonii, this new species differs by its light green leaflets at emergence (vs golden), leaflet imbricate to strongly imbricate (vs not imbricate), acuminate apex of microsporophylls (vs acute), tomentose indument and narrowly-triangular megasporophylls at maturity (vs pubescent at base or scarcely pubescent and triangular).

Comparison of leaflets of Dioon holmgrenii, D. stevensonii and Dioon nuusaviorum sp. nov.
A. D. stevensonii; B. D. holmgrenii; C. Dioon nuusaviorum sp. nov.;
D. D. stevensonii (F. Nicolalde-Morejón et al. 1554, CIB); E. D. holmgrenii (Brigada T. Walters s/n [3997], XAL); F. D. holmgrenii (F. Nicolalde-Morejón et al. 1468, XAL); G. Dioon nuusaviorum sp. nov. (L. Martínez-Domínguez et al. 1745, CIB).

 Lilí Martínez-Domínguez, Fernando Nicolalde-Morejón, Dennis Wm. Stevenson, Francisco G. Lorea-Hernández and Francisco Vergara-Silva. 2026. A striking New Species of Dioon (Zamiaceae) from pine and pine-oak forest of Guerrero, Mexico. PhytoKeys. 274: 229-245. DOI: doi.org/10.3897/phytokeys.274.173907 [11 May 2026]

[PaleoMammalogy • 2026] Cimolodon desosai • Cranial and Postcranial Remains of A New Species of Cimolodon (Multituberculata: Cimolodontidae) from the Upper Cretaceous (Campanian) El Gallo Formation of Baja California, México

Cimolodon desosai

Mantilla, Newbins, Fastovsky, Zhang, Montellano-Ballesteros, Alcántara & Chen, 2026

DOI: doi.org/10.1080/02724634.2026.2641109

Illustration by Andrey Atuchin

ABSTRACT

Late Cretaceous mammals from North America are predominantly known from isolated teeth and fragmentary jaws and from localities representing coastal lowlands along the Western Interior Seaway. Here, we report craniodental and associated postcranial remains of a new species of the cimolodontid multituberculate genus Cimolodon from the Upper Cretaceous (Campanian) El Gallo Formation of Baja California, México. The specimen was deposited along the Pacific Coast between 75.17 ± 0.30 Ma and 74.55 ± 0.18 Ma. It represents the most complete mammal known from the Mesozoic of México and one of the best known cimolodontan multituberculates from North America. Morphologically, the new species, Cimolodon desosai, is most like C. nitidus, but differences include upper anterior premolar shape, molar cusp formulae, and relative length proportions of the cheek teeth. Phylogenetic analysis supports placement of the new species within Cimolodon and Ptilodontoidea, but uncertainties remain regarding relationships among cimolodontan families. Using the craniodental and postcranial data, we quantitatively reconstruct C. desosai as a small-bodied (∼100 g), animal-dominated omnivore with a scansorial locomotor mode. With the new taxonomic occurrence, the El Gallo mammalian local fauna is now known from 16 specimens referred to three multituberculate species (Mesodma cf. M. formosa, ?Stygimys sp., and Cimolodon desosai), one metatherian (Pediomys sp.), and one eutherian (Gallolestes pachymandibularis). Although further sampling is needed, the mammalian local fauna presently shows greatest biogeographic affinities with the Terlingua local fauna of western Texas.

SYSTEMATIC PALEONTOLOGY

MAMMALIA Linnaeus, 1758

MULTITUBERCULATA Cope, 1884

CIMOLODONTA McKenna, 1975

PTILODONTOIDEA Sloan and Van Valen, 1965

CIMOLODONTIDAE McKenna, 1975

CIMOLODON Marsh, 1889

CIMOLODON DESOSAI, sp. nov.

Partial cranium of the holotype of Cimolodon desosai (IGM 14691).
Images are three-dimensional surface renderings from μCT scans in: A, anterior; B, stereo dorsal; C, stereo ventral; D, left lateral; and E, right lateral views of the partial cranium; and F, occlusal view of the right upper cheek tooth row in high magnification. Dashed white lines represent interpreted position of cranial bone sutures.

Abbreviations: al, anterior lamina; fr, frontal; iof, intraorbital foramen; mx, maxilla; na, nasal; naf, nasal foramen; otc, orbitotemporal canal; pa, parietal; pav, palatal vacuity; pmx, premaxilla; pop, postorbital process; sq, squamosal; zpm, zygomatic process of the maxilla. Scale bar equals 10 mm for A–E and 2 mm for F.

Cimolodon desosai on the tree with a fruit in its mouth. It was about the size of a golden hamster. It likely scampered on the ground and in the trees and ate fruits and insects.

Illustration by Andrey Atuchin

 

 

Gregory P. Wilson Mantilla, Isiah R. Newbins, David E. Fastovsky, Yue Zhang, Marisol Montellano-Ballesteros, Dalia García Alcántara and Meng Chen. 2026. Cranial and Postcranial Remains of A New Species of Cimolodon (Mammalia, Multituberculata, Cimolodontidae) from the Upper Cretaceous (Campanian) El Gallo Formation of Baja California, México. Journal of Vertebrate Paleontology. e2641109. DOI: doi.org/10.1080/02724634.2026.2641109  [22 Apr 2026]

[Botany • 2026] Echeveria zoquitlanensis (Crassulaceae) • A New microendemic Species from Oaxaca, Mexico

Echeveria zoquitlanensis J. Aragón-Parada & P. Carrillo,

in Aragón-Parada et Carrillo-Reyes. 2026. 

DOI: doi.org/10.17129/botsci.3802  

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Abstract

Background: Echeveria (Crassulaceae) is an American genus distributed from Mexico to South America. The genus has 132 species recorded in Mexico, where the state of Oaxaca with 56 species has the greatest richness of the genus. The exploration of the high mountains of Santa María Zoquitlán led us to discover a population of Echeveria that differed from previously known species.

Questions: Does the Echeveria population from the high areas of the municipality of Santa María Zoquitlán, Oaxaca represent a new species? 

Methods: Morphological comparison with the closely related taxa E. islasiae, E. longissima, E. longissima subsp. brachyantha, and E. longissima var. aztatlensis. Evaluation of conservation status based on the IUCN Red List categories and criteria.

Results: We described and illustrated Echeveria zoquitlanensis from Santa María Zoquitlán, Oaxaca, Mexico as a new species. Due their long corollas and styles, the new species were placed in the series Longistylae, mapped its distribution, and determined its conservation status category as critically endangered (CR B1; B2). It differs from the other members of the series by its very long (up to 3.7 cm) crimson red homochromatic flowers, and pale pink to red pistils.

Conclusions: Echeveria zoquitlanensis is the species with the largest flowers within the genus. Exploration carried out in isolated areas in Oaxaca favor the discovery of additional new species that would increase the large diversity of the state.

Keywords: endemism, New species, Sierra Madre del Sur, Zoquitlán, Saxifragales

Echeveria zoquitlanensis J. Aragón-Parada & P. Carrillo, sp. nov.

 

Juvenal Aragón-Parada and Pablo Carrillo-Reyes. 2026. Echeveria zoquitlanensis (Crassulaceae), A New microendemic Species from Oaxaca, Mexico.  Botanical Sciences. 104(2); 601-610. DOI: doi.org/10.17129/botsci.3802 [2026-04-01]

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[Paleontology • 2026] Prognathodon cipactli • A New Species of Prognathodon (Squamata: Mosasauridae) from the Early Maastrichtian of Nuevo León, Mexico

 

Prognathodon cipactli 

Rivera-Sylva, Sánchez-Uribe, Guzmán-Gutierrez, Rodríguez, Rangel-Morelos, & Longrich, 2026

 DOI: doi.org/10.1127/njgpa/1303

Abstract

Mosasaurs staged a major radiation at the end of the Cretaceous period before perishing at the Cretaceous-Paleogene boundary. Although mosasaurs are well-known from the Late Cretaceous of North America, relatively little is known about the mosasaurids of Mexico. In 2001 the largely complete skull of a mosasaurid was collected from outcrops of the Early Maastrichtian Mendez Formation at Rancho Las Barretas, 10 kilometers northeast of Linares. Although much of the skeleton was reported to have been present, only the skull was collected and the quarry has not been relocated. The specimen was described and figured in 2007 by Buchy et al. (2007) and reported as an indeterminate mosasaurid. Although the specimen has suffered some erosion after exposure in the desert, it includes most of the skull. We redescribe this specimen and show that it represents a derived species of Prognathodon, P. cipactli sp. nov. The specimen shows specializations for an apex predator niche, including a a short rostrum with robust jaws and teeth, suggesting that specialization for taking large prey preceded the evolution of large size in prognathodontins. The specimen enhances our understanding of the fossil record and paleoecology of the Western Interior Seaway during the Late Cretaceous, showing how prognathodontins successfully exploited the top predator niche globally in the Maastrichtian.  

Keywords: Mosasauridae • Prognathodon • Maastrichtian • Mexico • Mendez Formation

Prognathodon cipactli sp. nov. 

 

Rivera-Sylva, Héctor E.; Sánchez-Uribe, Iván E.; Guzmán-Gutierrez, José Rubén; Rodríguez, Rosalba Lizbeth Nava; Rangel-Morelos, Adolfo A. and Longrich, Nicholas. 2026. A New Species of Prognathodon (Squamata: Mosasauridae) from the Early Maastrichtian of Nuevo León, Mexico. Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen. DOI: doi.org/10.1127/njgpa/1303 [Mar 9, 2026]

[Botany • 2026] Peperomia accentus (Piperaceae) • A New geophytic Species endemic to the Sierra Madre Occidental, Mexico

Peperomia accentus Reveles & Amancio,

 in Hurtado-Reveles, Amancio et Burgos-Hernández, 2026. 

DOI: doi.org/10.11646/phytotaxa.740.3.2

 

Abstract

Peperomia accentus is described and illustrated as a new species of Piperaceae from the state of Zacatecas, Mexico, in the Sierra Madre Occidental mountain range. This new taxon belongs to the subgenus Tildenia, which includes species characterized by their geophytic habit. It can be distinguished from its congeners mainly by the combination of roots at the apex of the globose tuber, peltate leaves, numerous simple inflorescences and flowers with long and geniculated styles of a reddish color. A preliminary threat assessment is provided for the new species based on IUCN Red List guidelines. We provide a comprehensive analysis of the distribution patterns of the Mesoamerican species of Peperomia subgenus Tildenia. Finally, we include a key for species distributed north of the Trans-Mexican Volcanic Belt.

endemic, geophyte, Neotropics, Tildenia, Magnoliids

Peperomia accentus morphology. A. General view of a flowering specimen from a lateral perspective. B. General view from an upper perspective. C. Tuber from the bottom. D. Apex of a developing inflorescence with flowers in different anthesis stages. E. Flower with mature stamens from a front and bottom perspective. F. Close-up of a mature anther. G. Sideways perspective of a flower in anthesis. H. Closeup of a receptive stigma. I. Lateral perspective of a developing fruit.

Photographs of Peperomia accentus in habitat.
A. General view of a flowering specimen. B. Mature inflorescences. C. Closeup of a single inflorescence. D. Specimen growing in a sheltered soil pocket on a rock outcrop.

Peperomia accentus Reveles & Amancio, sp. nov. 

 

Diagnosis:—Peperomia accentus can be differentiated from the rest of the geophytic species of Peperomia subgenus Tildenia by the following combination of characters: globose tubers without trunk-like outgrowths, green to wine-colored inflorescences (green to black in sicco), and flowers with geniculate styles 1.5–2.5 mm long, which remain longer than the ovaries after anthesis, persistent in fruit. 

Etymology:—The specific epithet alludes to the common shape of the pistil in developing flowers: a wavy line which resembles a tilde (~). Tildes are graphemes commonly used as diacritic (accent) in several scripts.

Leopoldo HURTADO-REVELES, Guadalupe AMANCIO and Mireya BURGOS-HERNÁNDEZ. 2026. Peperomia accentus (Piperaceae), A New geophytic Species endemic to the Sierra Madre Occidental, Mexico.  Phytotaxa. 740(3); 237-247. DOI: doi.org/10.11646/phytotaxa.740.3.2 [2026-02-10]

[Botany • 2026] Hechtia mixtecana (Bromeliaceae: Hechtioideae) • A New Species from Oaxaca, Mexico

Hechtia mixtecana  Hern.-Cárdenas, Espejo & López-Ferr.,  

in Hernández-Cárdenas, Espejo- Serna, López- Ferrari, Lara- Godínez et Siekkinen, 2026. 

DOI: doi.org/10.1002/njb.05137 

Abstract

Botanical explorations carried out in the state of Oaxaca, Mexico, led to the discovery of a new Bromeliaceae: Hechtia mixtecana,which is here described and illustrated. The new taxon is compared with the morphologically similar Hechtia fragilis, Hechtia lyman-smithii, and Hechtia minuta. Hechtia mixtecana differs from these taxa by the orientation of the leaves (ascending to divaricate), by the architecture of the staminate (twice branched) and pistillate inflorescences (once to twice branched), and by the length of the primary branches of the pistillate inflorescence (15–28 cm). A complete morphological description, images, and a geographic distribution map of the new species are included, as well as a list of examined specimens.

Keywords: Balsas Basin Province, endemism, Monocots, Poales, Sierra Madre del Sur Province

Hechtia mixtecana sp. nov.
(a) Staminate and pistillate plants in bloom, (b) staminate primary branch, (c) staminate flower, (c1) floral bract, (c2) sepals, (c3) petals, (c4) stamens, (d) pistillate primary branch, (e) pistillate flower, (e1), floral bract, (e2) sepals, (e3) petals, (e4) pistil, (f) fruit, (g) seed. Illustration drawings a, b, c, d, e, f, g by M. T. Jiménez Segura; photographs c1–c4, e1–e4 by R. Hernández-Cárdenas.

Hechtia mixtecana sp. nov.
(a) Staminate flowers, (b) pistillate flowers. Photographs by R. Hernández-Cárdenas.

Hechtia mixtecana sp. nov. (a–b) Rosettes at the type locality.

Photographs by R. Hernández-Cárdenas.

Hechtia mixtecana Hern.-Cárdenas, Espejo & López-Ferr. sp. nov.  

Diagnosis: Hechtia mixtecana is similar to H. fragilis but differs in the inflorescence of the staminate plants (twice branched versus once branched), in the presence of indument on its peduncle and floral bracts (glabrous versus lepidote), in the shape (elliptic versus broadly ovate to oblong) of the petals of the staminate flowers; in the length of the primary branches of the pistillate plants (15–28 versus 1–6 cm), and in the presence of indument on its floral bracts (glabrous versus lepidote).

Etymology: The specific epithet refers to and honours the Mixtec culture from Mexico. One of the regions occupied by the Mixtec ethnic group is located in northwestern Oaxaca, the area in which the type locality of the new species is found.

Rodrigo Alejandro Hernández- Cárdenas, Adolfo Espejo- Serna, Ana Rosa López- Ferrari, Sofía Ana Lucrecia Lara- Godínez and Andrew Siekkinen. 2026. Hechtia mixtecana sp. nov. (Hechtioideae; Bromeliaceae), from Oaxaca, Mexico. Nordic Journal of Botany. DOI: doi.org/10.1002/njb.05137 [02 February 2026] 

[Botany • 2024] Megastigma acarrilloi (Rutaceae) • A New Species from Sinaloa, Mexico, with the northernmost distribution of the genus

Megastigma acarrilloi Pío-León,

in Pío-León, 2024. 

DOI: doi.org/10.21829/abm131.2024.2406 

Abstract

Background and Aims: The genus Megastigma has six described species of shrubs distributed from Colima, Mexico, to Nicaragua. Through a routine review of the iNaturalistMX platform in 2023, a record of an individual of the Megastigma genus was observed, although in a very disjunct locality with respect to known species. The collection and subsequent review of the specimens allowed us to determine that it was a new species for science.

Methods: Botanical explorations and collections were carried out during 2023 and 2024 in the Sierra de Barobampo, municipality of Ahome, Sinaloa, Mexico. The identity of the species was determined by the review of specialized literature. A map with the distribution of each species of the genus was elaborated using the available data in digital repositories and specimens in the MEXU herbarium. The conservation status of the new species was evaluated and proposed according to the IUCN criteria. An identification key is provided for all species of the genus Megastigma.

Results: Megastigma acarrilloi is endemic to northern Sinaloa, Mexico, and has the northernmost distribution of the genus. The species with the closest morphological affinity is M. morenoi, which is endemic to Colima, from which M. acarrilloi differs because it is glabrous and has fewer leaflets per leaf. During the explorations, Lepidopteran larvae of the genus Papilio were observed feeding on its leaves. It is recommended to include M. acarrilloi as a Vulnerable species (VU) on the IUCN Red List.

Conclusions: With the new species, the genus Megastigma is now integrated by seven species, all present in Mexico, and of which six are endemic to the country. Megastigma acarrilloi also represents the first record of the genus for Sinaloa and north of the Trans-Mexican Volcanic Belt.

Keywords: Barobampo mountains, endemism, iNaturalist, iNaturalistMX, Megastigma morenoi, Megastigma skinnerii

Megastigma acarrilloi Pío-León, sp. nov.

Juan Fernando Pío-León. 2024. Megastigma acarrilloi (Rutaceae), A New Species from Sinaloa, Mexico, with the northernmost distribution of the genus.  Acta Botanica Mexicana. 131; DOI: doi.org/10.21829/abm131.2024.2406 

[Paleontology • 2026] Xenovenator espinosai • A Thick-Skulled Troodontid Theropod (Maniraptora: Troodontidae) from the Late Cretaceous of Mexico

 

Xenovenator espinosai 

Rivera-Sylva, Aguillón-Martinez, Flores-Ventura, Sánchez-Uribe, Guzman-Gutierrez & Longrich, 2026

DOI: doi.org/10.3390/d18010038

Abstract

Dinosaurs repeatedly evolved adaptations for sexual selection over their 150-million year history, including adaptations for display and intraspecific combat. Adaptations for intraspecific combat have not previously been described in non-avian maniraptorans. We report a troodontid from the Campanian Cerro del Pueblo Formation of Coahuila, Mexico, showing a thickened and domed skull roof. The cranium is domed and bones are extremely thick, a morphology convergent on that of Pachycephalosauridae. Referred specimens show less thickening or doming, suggesting ontogenetic changes or perhaps sexual dimorphism. The holotype shows fusion of the frontal midline suture and tightly interdigitating sutures between skull bones, and a rugose skull roof. The specializations seen here suggest adaptation for intraspecific combat, specifically head-butting as hypothesized for pachycephalosaurids and pachyrhinosaurin ceratopsids. Repeated evolution of elaborate weapons and display features in the Cretaceous suggests that sexual selection became increasingly important in dinosaur evolution during the Cretaceous.

Keywords: Dinosauria; Theropoda; Maniraptora; Troodontidae; Cretaceous; Campanian; Laramidia; sexual selection; intraspecific combat

Saurischia Seeley, 1888 

Theropoda Marsh, 1881  

Avetheropoda Paul, 1988  

Coelurosauria Von Huene 1914  

Maniraptora Gauthier 1986  

Deinonychosauria Colbert and Russell, 1969 

Troodontidae Gilmore, 1924  

Troodontinae van der Reest and Currie, 2017 

Troodontini n. tax.

Xenovenator gen. nov.

Diagnosis. Troodontid characterized by thick frontals, anterior displacement of frontal postorbital processes relative to the parietal suture, broad and transversely arched interfrontal ridge, broad frontal-lacrimal suture.

Etymology. Greek xenos, ‘strange’ + Latin venator, ‘hunter’.

Xenovenator espinosai sp. nov. 

Holotype. CPC 2973, braincase including frontals, parietals, orbitosphenoids, laterosphenoids, exoccipitals, prootics, basisphenoid, basioccipital (Figure 4, Figure 5, Figure 6, Figure 7 and Figure 8).

 

Etymology. The species name honors Luis Espinosa, a pioneer in the study of Mexican dinosaurs and mentor to many generations of paleontologists.

Diagnosis. Xenovenator characterized by the following characters (* = autapomorphy): frontals extensively fused; frontals, parietals, and other cranial bones with strongly interdigitating sutures *; strong doming of frontals *; frontals and parietals massive (up to 12 mm thick) *, thickening well-developed anteriorly and less well-developed in the center of the frontal *; dorsal surface of frontals and parietals rugose and striated *, nasal processes broad between lacrimals *, orbital fossae widely separated ventrally *, frontal with notch and shelf to receive posterior end of lacrimal, parietal forms narrow process inserting between frontals *; triangular parietal table *, anteroventral expansion of the orbitosphenoids and laterosphenoids to enclose braincase ventrally *.

Horizon and Locality. Cerro Del Pueblo Formation, uppermost/latest Campanian (Figure 3), Coahuila, Mexico. CPC 2973 and CPC 3112 are from the La Parrita locality, 54 km west of Saltillo; municipality of General Cepeda, Coahuila, Mexico. CPC 3112 is from the Ejido Trincheras locality, 109 km west of Saltillo, municipality of Parras de la Fuente, Coahuila, Mexico (Figure 2).

 Hector E. Rivera-Sylva, Martha C. Aguillón-Martinez, Jose Flores-Ventura, Ivan E. Sánchez-Uribe, Jose Ruben Guzman-Gutierrez and Nicholas R. Longrich. 2026. A Thick-Skulled Troodontid Theropod from the Late Cretaceous of Mexico. Diversity. 18(1), 38. DOI: doi.org/10.3390/d18010038 [9 January 2026]

 

[PaleoBotany • 2026] Simojoflorum mijangosii gen. et sp. nov. preserved in the Mexican Amber unravels the polycarpellate condition in the tribe Mimoseae (Fabaceae: Caesalpinioideae)

  

Simojoflorum mijangosii 

Hernández-Damián, Rubalcava-Knoth, Gómez-Acevedo, Cruz-Durán & Cevallos-Ferriz, 

in Hernández-Damián, Knoth, Gómez-Acevedo, Cruz-Durán et Cevallos-Ferriz, 2026. 

DOI: doi.org/10.1080/08912963.2025.2604147

Drawings by Aldo Domínguez de la Torre.

 

ABSTRACT

An inflorescence preserved in amber from the middle-early Miocene from southern Mexico is identified as a new extinct member of Fabaceae. We described and identified the fossil material, comparing it with extant and fossil members of the Fabaceae using light microscopy and computed microtomography. The fossil inflorescence has morphological characters that allow a near comparison with Caesalpinioideae (Fabaceae), including flowers aggregated in a capitate inflorescence. Even more, bisexual and staminate flowers, valvate aestivation, many stamens, a superior, unilocular ovary with marginal placentation are characters that allow their comparison with the tribe Mimoseae, especially the polycarpellate gynoecium is comparable to the Acacieae and Ingeae tribes in the traditional classification. However, other floral characteristics, such as anther glands, partially united filaments, a basal nectariferous disk, and a stalk ovary, are comparable to Mariosousa Seigler & Ebinger, 2006, Senegalia Raf., 1838, and Parasenegalia Seigler & Ebinger, 2017. The phylogenetic relationship between them is unresolved, and information on the floral structure is limited for further comparison. Thus, we support the identification of Simojoflorum mijangosii gen. et sp. nov. as a new extinct member of the tribe Mimoseae that suggests the diversification of the lineage during the Miocene.

KEYWORDS: Fossil inflorescence, Fabaceae, Mimoseae, Miocene, polycarpellate

Simojoflorum mijangosii gen. et sp. nov. from Simojovel de Allende, Chiapas, Mexico.
(A) Overall view showing the spherical capitate inflorescence, scale bar: 1.0 mm. (B), Lateral view of spherical inflorescence, scale: 1.0 mm. (C) Detail of staminate and bisexual flowers arranged in the spherical capitate inflorescence, inferior left arrow indicates staminate flower, superior left arrow indicates the differentiated perianth, and right arrow indicates a bisexual flower with a large style, scale: 1.0 mm. (D) Detail of sessile flowers with differentiate perianth, right arrow indicates sepal and left arrow to indicate petal, scale: 0.5 mm. (E) Detail of anthers, right arrow indicates dorsifixed anthers, and left arrow indicates glandular appendage, scale: 0.2 mm. (F) Detail of stigma and style, scale: 0.5 mm.

Family: Fabaceae Lindley, Citation1836

Subfamily Caesalpinioideae De Candolle, Citation1825

Tribe: Mimoseae sensu Queiroz et al. Citation2024

Genus: Simojoflorum Hernández-Damián, Rubalcava-Knoth, Gómez-Acevedo, Cruz-Durán et Cevallos-Ferriz gen. nov.

Etymology: The epithet Simojo refers to Simojovel de Allende, the locality from which the fossil was collected, and florum, of Latin meaning flowers.

Generic diagnosis: Inflorescence capitate and spherical with staminate and bisexual flowers. Staminate flowers sessile with pentamerous and differentiate perianth, actinomorphic; calyx and corolla with valvate aestivation, androecium with more than 30 stamens slightly fused at the base with stalked glands. Bisexual flowers with a basal nectariferous disk; central carpel stipitate, ovary superior, unilocular with ca. twenty ovules in two rows, and marginal placentation along a ventral suture. Some bisexual flowers present 4–5 peripheral carpels that surround the central carpel, these carpels are poorly differen and smaller than the central one.

 

Simojoflorum mijangosii Hernández-Damián, Rubalcava-Knoth, Gómez-Acevedo, Cruz-Durán et Cevallos-Ferriz sp. nov.

Etymology: The epithet mijangosii refers to Luis Alonso Zuñiga Mijangos who contributed to the study of Mexican amber through the Museo del ámbar, Lilia Mijangos.

 

Holotype: MALM-00111 (Museo del Ámbar, Lilia Mijangos)

 

Locality: Simojovel de Allende, Chiapas, Mexico

Stratigraphic horizon: La Quinta Formation, middle-early Miocene

Artistic reconstruction of inflorescence, flowers, and hypothetical whole plant of Simojoflorum mijangosii gen. et sp. nov. in the Mexican amber.
(A) Spherical capitate inflorescence of Simojoflorum mijangosii, scale=1.0 mm. (B) Details of staminate flower, scale = 0.25 mm. (C) Details of anther glands, scale=0.05 mm. (D) Details of monocarpellate bisexual flower, scale = 0.25 mm; (E) Details of polycarpellate bisexual flower, scale = 0.25 mm. (F) Hypothetical Simojoflorum mijangosii small tree, scale = 2.0 m.

Drawings by Aldo Domínguez de la Torre.

 Ana L. Hernández-Damián, Marco A. Rubalcava Knoth,Sandra L. Gómez- Acevedo, Ramiro Cruz-Durán and Sergio R. S. Cevallos-Ferriz. 2026. Simojoflorum mijangosii gen. et sp. nov. preserved in the Mexican Amber unravels the polycarpellate condition in the tribe Mimoseae (Caesalpinioideae, Fabaceae). Historical Biology: An International Journal of Paleobiology. DOI: doi.org/10.1080/08912963.2025.2604147 [13 Jan 2026]

[Botany • 2020] Graptopetalum sinaloensis (Crassulaceae) • A New Species from Sinaloa, Mexico

Graptopetalum sinaloensis R. Vega, 

 in Vega Aviña, Vargas et Pío León, 2020.  

DOI: 10.21829/abm127.2020.1550 

  Researchgate.net/publication/345773954

ABSTRACT 

Background and Aims: The genus Graptopetalum includes about 20 species of branched or acaulescent rosette herbs that grew in little accessible semiarid environments (mountains or ravines) of Mexico and Arizona. The authors have developed continuous work to document the flora of Sinaloa and the present article reports a taxonomic novelty in the genus Graptopetalum.

Methods: In the municipality of Culiacán, Sinaloa, Mexico, a small population of plants of the genus Graptopetalum with dry inflorescences was found in June 2013, and some plants were collected and cultivated, they flowered in March. Plants with flowers were collected from the same location in February 2014. Morphological data of wild and cultivated material were compared with that of herbarium specimens, literature, and cultivated Graptopetalum species; and it was determined that collected material is a new species for science.

Key results: The new taxon Graptopetalum sinaloensis, section Graptopetalum, is described. Its differences and similarities with the closest species are discussed. Moreover, a new and updated dichotomous key is provided for the eight species of this section.

Conclusions: Graptopetalum sinaloensis is endemic to south-central Sinaloa, Mexico. It grows in very localized areas, on rocky walls of streams and at the foot of hills, forming small populations in reduced areas of 5 to 10 m2. Graptopetalum sinaloensis differs from other Graptopetalum species from Sinaloa by its 5-merous flowers vs. G. rusbyi with 6-7-merous ones, and by its paniculate inflorescence, vs. G. occidentale with cymose ones. Additionally, the geographical distribution of the three species does not overlap.

Key words: Byrnesia, flora of Sinaloa, Graptopetalum rusbyi, Graptopetalum occidentale, Sedum, tropical deciduous forest.

Graptopetalum sinaloensis R. Vega.
A. plantas colectadas en campo (28.II.2014); B. y C. inflorescencias y planta en floración en medio silvestre (3.III.2019); D. planta sin floración registrada (7.XI.2018).

Fotos de Rito Vega-Aviña (A) y Juan Fernando Pío-León (B-D).

Graptopetalum sinaloensis R. Vega, sp. nov.

Rito Vega Aviña, Francisco Delgado Vargas and Juan Fernando Pío León. 2020. Graptopetalum sinaloensis (Crassulaceae), una nueva especie de Sinaloa, México [Graptopetalum sinaloensis (Crassulaceae), A New Species from Sinaloa, Mexico]. Acta Botanica Mexicana. 127; e1550. DOI: 10.21829/abm127.2020.1550 

 Researchgate.net/publication/345773954_Graptopetalum_sinaloensis_una_nueva_especie_de_Sinaloa_Mexico

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