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Issue: Vol. 9 No. 2: 29 Apr. 2026
Type: Article
Published: 2026-04-29
DOI: 10.11646/palaeoentomology.9.2.10
Page range: 182-188
Abstract views: 44
PDF downloaded: 9

First record of a four-tepaled flower of Tropidogyne from mid-Cretaceous Kachin amber

State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China, University of Chinese Academy of Sciences, Beijing 100049, China
State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China
State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China
State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China, University of Chinese Academy of Sciences, Beijing 100049, China
eudicots floral variation fossil Myanmar

Abstract

The establishment of a fixed pentamerous floral ground plan was a key innovation in the radiation of core eudicots (Pentapetalae). However, the developmental stability of this trait during the Cretaceous Angiosperm Terrestrial Revolution (ATR) remains poorly understood. Tropidogyne, a dominant flower genus in the mid-Cretaceous Kachin amber, has been previously characterized by a predominantly pentamerous organization and a striking morphological resemblance to the extant family Cunoniaceae (e.g., Ceratopetalum). Here, we report a unique four-tepaled flower assigned to Tropidogyne cf. pentaptera. The reduction from five to four tepals is accompanied by a coordinated decrease in ovary ridges (from ten to eight), suggesting a developmental variation. While this meristic instability is comparable to variation observed in extant Ceratopetalum, the absence of diagnostic cunoniaceous synapomorphies suggests that Tropidogyne likely belongs to an unresolved lineage within rosids. This finding indicates that variability in floral organ number was already present in mid-Cretaceous eudicots. This pattern may reflect developmental plasticity in early eudicot ontogeny and provides new insights into the stabilization of the pentamerous floral ground plan in extant lineages.

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