The fossil record of Eucalyptus in Patagonia

HEMSEN, GANDOLFO, ZAMALOA

AMERICAN JOURNAL OF BOTANY

BOTANICAL SOC AMER INC

Año: 2012 vol. 99 p. 1356 - 1374

0002-9122

Premise of the study: Herein, we name, describe, and illustrate new macrofossil material representing Eucalyptus (Myrtaceae: Myrtoideae, Eucalypteae) from the diverse early Eocene Laguna del Hunco (LH) fl ora of Chubut Province, Patagonia, Argentina. We explore the signifi cance of these fossils in light of understanding the fossil record of eucalypts and the biogeography of the Eucalypteae. ? Methods: Fossils representing vegetative and reproductive organs were collected from multiple LH localities over several fi eld seasons. These specimens were prepared, photographed, and compared to extant Eucalyptus . Additional historical collections of Patagonian fossil Eucalyptus were also examined. ? Key results: Vegetative and reproductive organs representing fi ve different Eucalyptus taxa were identifi ed in the LH paleofl ora. One new taxon each representing leaves, fl ower buds, and infructescences with co-occurring, isolated capsules are described and named as new Eucalyptus species. Additionally, two fl ower types cf. Eucalyptus , represented by one specimen each, are illustrated and briefl y described. The fossil species have unique characteristics that independently suggest each belongs within the Eucalypteae. The reproductive material is most similar morphologically to extant Eucalyptus , although it also shares many similarities to the closely related genus Corymbia . ? Conclusions: The LH fossil Eucalyptus material is among the few eucalypt macrofossils that have recently been named and described and are the oldest macrofossils that can presently be defi nitively ascribed to the Eucalypteae. They also represent the only credible description of Eucalyptus fossils occurring outside of Australasia and suggest a once broader geographic distribution for this group.Herein, we name, describe, and illustrate new macrofossil material representing Eucalyptus (Myrtaceae: Myrtoideae, Eucalypteae) from the diverse early Eocene Laguna del Hunco (LH) fl ora of Chubut Province, Patagonia, Argentina. We explore the signifi cance of these fossils in light of understanding the fossil record of eucalypts and the biogeography of the Eucalypteae. ? Methods: Fossils representing vegetative and reproductive organs were collected from multiple LH localities over several fi eld seasons. These specimens were prepared, photographed, and compared to extant Eucalyptus . Additional historical collections of Patagonian fossil Eucalyptus were also examined. ? Key results: Vegetative and reproductive organs representing fi ve different Eucalyptus taxa were identifi ed in the LH paleofl ora. One new taxon each representing leaves, fl ower buds, and infructescences with co-occurring, isolated capsules are described and named as new Eucalyptus species. Additionally, two fl ower types cf. Eucalyptus , represented by one specimen each, are illustrated and briefl y described. The fossil species have unique characteristics that independently suggest each belongs within the Eucalypteae. The reproductive material is most similar morphologically to extant Eucalyptus , although it also shares many similarities to the closely related genus Corymbia . ? Conclusions: The LH fossil Eucalyptus material is among the few eucalypt macrofossils that have recently been named and described and are the oldest macrofossils that can presently be defi nitively ascribed to the Eucalypteae. They also represent the only credible description of Eucalyptus fossils occurring outside of Australasia and suggest a once broader geographic distribution for this group.Methods: Fossils representing vegetative and reproductive organs were collected from multiple LH localities over several fi eld seasons. These specimens were prepared, photographed, and compared to extant Eucalyptus . Additional historical collections of Patagonian fossil Eucalyptus were also examined. ? Key results: Vegetative and reproductive organs representing fi ve different Eucalyptus taxa were identifi ed in the LH paleofl ora. One new taxon each representing leaves, fl ower buds, and infructescences with co-occurring, isolated capsules are described and named as new Eucalyptus species. Additionally, two fl ower types cf. Eucalyptus , represented by one specimen each, are illustrated and briefl y described. The fossil species have unique characteristics that independently suggest each belongs within the Eucalypteae. The reproductive material is most similar morphologically to extant Eucalyptus , although it also shares many similarities to the closely related genus Corymbia . ? Conclusions: The LH fossil Eucalyptus material is among the few eucalypt macrofossils that have recently been named and described and are the oldest macrofossils that can presently be defi nitively ascribed to the Eucalypteae. They also represent the only credible description of Eucalyptus fossils occurring outside of Australasia and suggest a once broader geographic distribution for this group.Eucalyptus . Additional historical collections of Patagonian fossil Eucalyptus were also examined. ? Key results: Vegetative and reproductive organs representing fi ve different Eucalyptus taxa were identifi ed in the LH paleofl ora. One new taxon each representing leaves, fl ower buds, and infructescences with co-occurring, isolated capsules are described and named as new Eucalyptus species. Additionally, two fl ower types cf. Eucalyptus , represented by one specimen each, are illustrated and briefl y described. The fossil species have unique characteristics that independently suggest each belongs within the Eucalypteae. The reproductive material is most similar morphologically to extant Eucalyptus , although it also shares many similarities to the closely related genus Corymbia . ? Conclusions: The LH fossil Eucalyptus material is among the few eucalypt macrofossils that have recently been named and described and are the oldest macrofossils that can presently be defi nitively ascribed to the Eucalypteae. They also represent the only credible description of Eucalyptus fossils occurring outside of Australasia and suggest a once broader geographic distribution for this group.Eucalyptus were also examined. ? Key results: Vegetative and reproductive organs representing fi ve different Eucalyptus taxa were identifi ed in the LH paleofl ora. One new taxon each representing leaves, fl ower buds, and infructescences with co-occurring, isolated capsules are described and named as new Eucalyptus species. Additionally, two fl ower types cf. Eucalyptus , represented by one specimen each, are illustrated and briefl y described. The fossil species have unique characteristics that independently suggest each belongs within the Eucalypteae. The reproductive material is most similar morphologically to extant Eucalyptus , although it also shares many similarities to the closely related genus Corymbia . ? Conclusions: The LH fossil Eucalyptus material is among the few eucalypt macrofossils that have recently been named and described and are the oldest macrofossils that can presently be defi nitively ascribed to the Eucalypteae. They also represent the only credible description of Eucalyptus fossils occurring outside of Australasia and suggest a once broader geographic distribution for this group.Key results: Vegetative and reproductive organs representing fi ve different Eucalyptus taxa were identifi ed in the LH paleofl ora. One new taxon each representing leaves, fl ower buds, and infructescences with co-occurring, isolated capsules are described and named as new Eucalyptus species. Additionally, two fl ower types cf. Eucalyptus , represented by one specimen each, are illustrated and briefl y described. The fossil species have unique characteristics that independently suggest each belongs within the Eucalypteae. The reproductive material is most similar morphologically to extant Eucalyptus , although it also shares many similarities to the closely related genus Corymbia . ? Conclusions: The LH fossil Eucalyptus material is among the few eucalypt macrofossils that have recently been named and described and are the oldest macrofossils that can presently be defi nitively ascribed to the Eucalypteae. They also represent the only credible description of Eucalyptus fossils occurring outside of Australasia and suggest a once broader geographic distribution for this group.Eucalyptus species. Additionally, two fl ower types cf. Eucalyptus , represented by one specimen each, are illustrated and briefl y described. The fossil species have unique characteristics that independently suggest each belongs within the Eucalypteae. The reproductive material is most similar morphologically to extant Eucalyptus , although it also shares many similarities to the closely related genus Corymbia . ? Conclusions: The LH fossil Eucalyptus material is among the few eucalypt macrofossils that have recently been named and described and are the oldest macrofossils that can presently be defi nitively ascribed to the Eucalypteae. They also represent the only credible description of Eucalyptus fossils occurring outside of Australasia and suggest a once broader geographic distribution for this group.Eucalyptus , although it also shares many similarities to the closely related genus Corymbia . ? Conclusions: The LH fossil Eucalyptus material is among the few eucalypt macrofossils that have recently been named and described and are the oldest macrofossils that can presently be defi nitively ascribed to the Eucalypteae. They also represent the only credible description of Eucalyptus fossils occurring outside of Australasia and suggest a once broader geographic distribution for this group.Corymbia . ? Conclusions: The LH fossil Eucalyptus material is among the few eucalypt macrofossils that have recently been named and described and are the oldest macrofossils that can presently be defi nitively ascribed to the Eucalypteae. They also represent the only credible description of Eucalyptus fossils occurring outside of Australasia and suggest a once broader geographic distribution for this group.Conclusions: The LH fossil Eucalyptus material is among the few eucalypt macrofossils that have recently been named and described and are the oldest macrofossils that can presently be defi nitively ascribed to the Eucalypteae. They also represent the only credible description of Eucalyptus fossils occurring outside of Australasia and suggest a once broader geographic distribution for this group.Eucalyptus fossils occurring outside of Australasia and suggest a once broader geographic distribution for this group.