Anatomy and development of fruits of Lauraceae from the Middle Eocene Princeton Chert

Abstract

Investigations of the Middle Eocene Princeton Chert reveal evidence for the connection of lauraceous flowers to fruits through a developmental series. Youngest fruits are found with attached floral remnants. Later stages show receptacle enlargement, fruit wall thickening, and the development of abundant sclereid clusters. Mature fruits are borne on a shallow receptacle and have an endocarp palisade layer of radially elongate cells with stellate outlines, an inner mesocarp layer of radiately arranged sclereid clusters, and a fleshy outer mesocarp layer containing numerous idioblasts with contents. Each mature fruit bears a single seed retaining the outer integument with an innermost radially elongate transfusion cell layer. Mature seeds contain a cellular embryo bearing idioblasts. Fruits are distinguishable from previously described anatomically preserved fossil taxa. This study represents the only documented developmental reconstruction of fossil fruits of Lauraceae and that self-pruning evolved prior to the Eocene. Anatomical modifications over the developmental sequence indicate that different stages of maturity preserved together, may be erroneously identified as several taxa at a fossil locality. Fossil morphotypes typically underestimate species number, but this study suggests that the number of inferred species based on fruit types may be inflated for Lauraceae, potentially exaggerating the tropical interpretation of the paleoenvironment.

Subcellular Lipid Droplets in Vanilla Leaf Epidermis and Avocado Mesocarp Are Coated with Oleosins of Distinct Phylogenic Lineages

“…A fat cell has one to several large LDs of 5-mm to 20-mm diameter, whereas an oil cell has one large oil drop occupying most of the cell volume. Litsea and Lindera species and other members of Lauraceae also have fruit morphology similar to that of avocado (Little et al, 2009).…”

A review of paleobotanical studies of the Early Eocene Okanagan (Okanogan) Highlands floras of British Columbia, Canada, and Washington, USA

“…Initial radiometric dates of 49-50 Ma were based on the K-Ar method for volcanic sediments at Allenby near the chert site (Hills and Baadsgaard 1967). Little et al (2009) (also see DeVore and Pigg 2010) cite an unpublished radiometric date of 48.7 Ma (without an age uncertainty value) for ash layer #22 in the Princeton chert, placing the Princeton chert as latest Early Eocene (i.e., Early-Middle Eocene boundary at 47.8 Ma; Cohen et al 2013) (Fig. 3).…”

“…Small lauraceous flowers and fruits (Little et al 2009), flowers of Piperales (Smith and Stockey 2007), and fruits and seeds of Paleomyrtinaea (Myrtaceae, Pigg et al 1993) are often associated with the aquatic plant remains.…”

Floristic composition and comparison of middle Eocene to late Eocene and Oligocene floras in North America

“…Stratigraphically, the chert is found within the Princeton Group, Allenby Formation, and was initially dated as middle Eocene by Hills & Baadsgaard (1967) using potassium argon dating. A recently resampled date obtained by Baadsgaard was 48.7 Ma from ash layer # 22 (see Little et al 2009). …”

“…This locality consists of 49 interbedded chert and coal layers with occasional ash beds. Some of the cherts split and anastomose, resulting in around 70 layers altogether (Little et al 2009). Stratigraphically, the chert is found within the Princeton Group, Allenby Formation, and was initially dated as middle Eocene by Hills & Baadsgaard (1967) using potassium argon dating.…”