The First Fossil Record of Coryphoid Palm from Siwalik Strata (Middle Miocene) of Darjeeling Foothills of Eastern Himalaya

IF 0.7 4区 地球科学 Q4 PALEONTOLOGY
S. Mahato, M. A. Khan
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Abstract

Although coryphoid fossil palms are well-known from the Upper Cretaceous sediments of India, there is no fossil evidence of coryphoid palms from Siwalik sediments to date. Here, we report for the first time coryphoid palm fronds from the lower Siwalik strata (Chunabati Formation; middle Miocene) of Darjeeling foothills of eastern Himalaya. The leaf architecture, as well as the epidermal anatomy of the Siwalik specimens, suggests their resemblance with those of extant members of the palm sub-family Coryphoideae. The Siwalik specimens are characterized morphologically by palmate fan-shaped leaf with a well-preserved costa (costapalmate), prominent leaf segments emerging at an acute angle from the costa, numerous parallel secondary lateral veins on either side of the mid-vein, and anatomically by hypostomatic leaf blade, rectangular to polygonal epidermal cells, cyclocytic type of stomata and the presence of characteristic trichome bases. Based on a thorough comparison with earlier reported coryphoid palm leaves bearing epidermal anatomy, we placed our specimens under a new fossil species Sabalites siwalicus sp. nov. that is also supported by cluster analysis. The present fossils indicate that coryphoid palms were present in eastern Himalaya by the Siwalik time and they experienced a warm and humid tropical environment during the time of deposition.

Abstract Image

东喜马拉雅大吉岭山麓西瓦利克地层(中新世)首次记录的蝶形棕榈化石
摘要尽管印度上白垩统沉积物中的蝶形棕榈化石已广为人知,但迄今为止还没有从西瓦利克沉积物中发现蝶形棕榈化石的证据。在此,我们首次报告了喜马拉雅山东部大吉岭山麓的下西瓦利克地层(Chunabati Formation;中新世中期)中的蝶形棕榈叶片。西瓦利克标本的叶片结构和表皮解剖表明,它们与现存的棕榈亚科苣苔属植物的叶片结构和表皮解剖相似。Siwalik 标本的形态特征是掌状扇形叶,叶缘保存完好(叶缘),突出的叶片从叶缘呈锐角出现,中脉两侧有许多平行的次侧脉;解剖特征是叶片下位,表皮细胞呈矩形至多边形,气孔呈环状,并有特征性的毛状体基部。根据与早期报道的具有表皮解剖结构的蝶形棕榈叶片的全面比较,我们将标本归入新的化石物种 Sabalites siwalicus sp.目前的化石表明,喜马拉雅东部早在西瓦利克时期就出现了蝶形花棕榈,它们在沉积期间经历了温暖潮湿的热带环境。
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来源期刊
Paleontological Journal
Paleontological Journal 地学-古生物学
CiteScore
1.20
自引率
33.30%
发文量
70
审稿时长
6-12 weeks
期刊介绍: Paleontological Journal (Paleontologicheskii zhurnal) is the principal Russian periodical in paleontology. The journal publishes original work on the anatomy, morphology, and taxonomy of fossil organisms, as well as their distribution, ecology, and origin. It also publishes studies on the evolution of organisms, ecosystems, and the biosphere and provides invaluable information on global biostratigraphy with an emphasis on Eastern Europe and Asia.
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