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| Simojoflorum mijangosii Hernández-Damián, Rubalcava-Knoth, Gómez-Acevedo, Cruz-Durán & Cevallos-Ferriz, in Hernández-Damián, Knoth, Gómez-Acevedo, Cruz-Durán et Cevallos-Ferriz, 2026. 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
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| 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
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| 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]
