Abstract Detail


Sender, Luis Miguel [1], Doyle, James [2], Endress, Peter [3], Diez, José Bienvenido [4], Villanueva, Uxue [5].

Evidence on vegetative and inflorescence morphology of Chloranthaceae from the Early Cretaceous (middle-late Albian) of Spain.

Chloranthaceae are one of five major clades making up the Mesangiospermae, which include ca. 99.9% of living angiosperm species, together with magnoliids, monocots, eudicots, and Ceratophyllum. Phylogenetic analyses of molecular and morphological data indicate that their sister group is either magnoliids or Ceratophyllum. Today Chloranthaceae consist of four genera and ca. 75 species, but they were one of the most common angiosperm groups in the Early Cretaceous fossil record. Dispersed reticulate-columellar monosulcate pollen assigned to Clavatipollenites, Asteropollis, and Retimonocolpites has long been compared with Chloranthaceae and is associated with a growing number of Albian and Cenomanian floral mesofossil taxa, some clearly nested within the crown group of the family (Hedyflora, Canrightiopsis), others attached to its stem lineage (Canrightia, possibly Zlatkocarpus). There are also Cretaceous leaves with chloranthoid teeth and other characters of the family, but because these features also occur in other “basal” groups the assignment of such leaves to Chloranthaceae has been tentative. Here we report several impression specimens of branches bearing leaves and in one case axillary inflorescences from the Alcaine locality in the Upper Member of the Escucha Formation (middle or late Albian) in Teruel Province, northeastern Spain, plus many isolated chloranthoid leaves. The branches show the opposite phyllotaxis and characteristic swollen nodes, fused sheathing leaf bases, and paired interpetiolar stipules of extant Chloranthaceae. The architecture of the attached leaves is most comparable to the Early Cretaceous fossil-genus Quercophyllum, which suggests a relationship to the Sarcandra-Chloranthus clade rather than Hedyosmum or Ascarina, but some isolated leaves are different. The inflorescences are compound spikes bearing three-lobed structures whose morphology is still uncertain because of the lack of organic preservation in the observed material. The lobes may represent three stamens attached to a carpel, as in Chloranthus, Late Cretaceous Chloranthistemon flowers, and the early Albian flower Canrightiopsis, which phylogenetic analyses attach to the stem lineage of Sarcandra and Chloranthus. No pollen is preserved at the Alcaine locality, but the chloranthoid pollen types Clavatipollenites, Asteropollis, and Hammenia occur in the Upper Member at other sites in the same basin. These observations are the first direct evidence, based on organically connected parts, for the distinctive vegetative morphology and inflorescence structure of crown-group Chloranthaceae in the Early Cretaceous and are consistent with the level of diversification within the family inferred from pollen and floral mesofossils.

1 - Universidad de Zaragoza, Departamento de Ciencias de la Tierra, Zaragoza, 50009, Spain
2 - University Of California Davis, DEPT OF EVOL & ECOLOGY, One Shields Avenue, Davis, CA, 95616, United States
3 - University of Zurich, Department of Systematic and Evolutionary Botany, Zurich, 8008, Switzerland
4 - Universidade de Vigo, Xeociencias Mariñas e Ordenación do Territorio, Vigo, 36310, Spain
5 - Estación Regional del Noroeste, UNAM, Instituto de Geología, Hermosillo, Sonora, 83000, Mexico

Leaf evolution

Presentation Type: Oral Paper
Number: 0002
Abstract ID:867
Candidate for Awards:None

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