Notes on Fossil Fruits

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Introduction

Fossil material of plants can be difficult to identify as to species, genus, or larger taxonomic units, as usually what is found is individual parts of plants, such as wood, leaves, flowers, fruits or pollen, and these are often insufficient for identification, particularly for older material why is less closely related to modern material, and may be less well preserved. Consequently, and as fossils of one plant part often cannot be unambigiously associated with those of another plant part, palaeobotanists use form genera to classify parts of plants of uncertain taxonomic position. The suffices -carpon, -carpum and -carpus are often used in generic names, indicating a similarity with the fruits of the modern genus whose name is combined with that suffix. It cannot be assumed that the fossil fruits represent a species particularly close to the modern genus; for example Craigia bronnii fruits were earlier interpreted as rutaceous or sapindaceous, and Nordenskioldia borealis and Sterculiocarpus coloradensis have been transferred to Trochodendraceae and Papaveraceae respectively.

I suspect that the genera and species of fossil malvaceous fruits listed below are far from an exhaustive coverage. Furthermore fossil fruits may be ascribed to a living genus, and this will be even harder to track down.

Carpolithes bowerbanki (Carpolithes is a catchall for fossil fruits of uncertain affinity) may be malvaceous.

Cantitilia

Cantitilia ("Kentish Lime") is a fossil genus known from seeds found in the Eocene London Clay strata of northern Kent (Isle of Sheppey and Herne Bay). On the basis of a detailed microstructural analysis Read and Chandler classify this genus as closely related to Tilia. Cantitilia differs from Tilia in having more (5) ovules in an ovary locule, and in the mature fruit being 2–3-seeded (most ovules not maturing), as opposed to the single-seeded state characteristic of Tilia.

The seeds of Cantitilia are syncarpous capsules. They are (4–)5-locular, many-ovulate, but with few maturing seeds, with axile placentation, and loculicidal dehiscence.

There are two known species (as of 1961), C. polysperma Reid and Chandler, and C. lobata Chandler. The fruits of the former are ovoid, 6½-13 mm long, 5-11½ mm wide, with seeds 4 to 5 mm long, 3 to 5½ mm wide. The fruits of the latter are deeply 5-lobed, 6 cm long by 11 mm across, with seeds about 4½ mm long and 3¾ mm broad.

Christianocarpum

Christianocarpum is a form genus representing fossil fruits similar to those of the living genus Chrisitiana,

Christianocarpum quinquelocularis, from the Eocene of France, is interpreted as belonging to a plant which belongs to the genus Christiana.

Daberocarpon

Daberocarpon is a presumed malvaceous fruit. Daberocarpon gerhardii is based on a 10-locular fruit from the uppermost Cretaceous of the Deccan Intratrappean Beds of India [a].

Malvacarpus

Malvacarpus is a form genus representing fossil fruits similar to those of extant mallows.

The species Malvacarpus guiñazui Berry is recorded from the Palaeocene or Eocene of the Rio Negro region of Argentina.

Hightea

Hightea is a fruit fossil, assigned to Malvaceae, from the Eocene of Britain. Species include Hightea elliptica, Hightea orbicularis, Hightea oviformis, Hightea turbinata and Hightea turgida.

Nordenskioldia

Nordenskioldia is a fruit fossil once assigned to Tiliaceae, but now considered as a member of Trochodedraceae, with an extensive fossil record in time (Palaeocene to Miocene) and space (North America, Greenland, Scotland, Spitzbergen, Russia, Inner Mongolia). The leaf genus Zizyphiodes is thought to represent the same plant.

Pentaloculocarpon

Pentaloculocarpon chitaleii Kapgate & Kapgate is a fruit fossil from the Intertrappean beds of the Deccan, which may be malvaceous. It is a pentalocular loculicidal capsule with axile placentation and single-seeded locules, of ovoid shape measuring 850µ by 1mm. The pericarp is differentiated into a outer thin epidermal zone, followed by middle multilayered parenchymatous zone consisting intercellular spaces and mucilage canals, followed by 1-2 layered compact inner zone. The seed has a membranous coat. The embryo isdicotyledonous and embedded in endosperm tissue.

Pteleaecarpum

Pteleaecarpum is a form genus representing fossil fruit mistakenly interpreted as related to those of Ptelea (Rutaceae). However Pteleaecarpum bronnii is now recognised as being the fruit of a species of Craigia (Tilieae), of which floral and foliar material is also available [c]. Pteleaecarpum europeum represents the same species [2]. Fossil material of Craigia bronnii is known from several localities in Europe, including the Lower Oligocene of Hungary, the Lower Miocene of Bohemia, and the Upper Miocene of Germany

Sphinxia

Sphinxia ovalis is a fossil fruit from the Londay Clay interpreted as being Dombeyoid, and most closely allied to Dombeya and Trochetia. (The name Sphinxia is also applied to a Devonian lycopsid; one or other usage of this generic name will be invalid.)

Sterculia

Fruit assigned to Sterculia palaeovillosa on the grounds of its siimilarity to the living Sterculia villosa is recorded from the Oligocene of Assam [1].

Sterculiocarpus

Sterculiocarpus is a form genus representing fossil fruits similar to those of living Sterculia.

The species Sterculiocarpus coloradensis Berry has been reduced to synonyny with Palaeoaster porosa (Papaveraceae) [b]. Leaf material named Sterculia coloradensis consists of deeply three lobed leaves that don't present a papaveraceous aspect, and presumably does not represent the same taxon.

Other names which has been published are Sterculiocarpus eocenicus Berry and Sterculiocarpus sphericus Berry, from the Eocene Wilcox Fm, and Sterculiocarpus sezannelloides Berry from the Eocene Lagrange Fm. I do not know whether these represent genuine sterculioid fruits.

References

  1. Mehrota, Two new fossil fruits from Oligocene sediments of Makum Coalfield, Assam, India, Current Science 79(10): 1482-1483 (2000)
  2. Kvacek, Early Miocene records of Craigia (Malvaceae s.l.) in the Most Basin, North Bohemia - whole plant approach, Journal of the Czech Geological Society 49(3/4): 161-171 (2004)

Bibliography

  1. S. D. Chitaley and M. T. Sheikh, A ten locular petrified fruit from the Deccan Intertrappean Series of India, The Palaeobotanist 20(3): 297-299 (1973)
  2. Una R. Smith, Strange fruit of the Cretaceous poppy (in Sixth North American paleontological convention; abstracts of papers, Repetski,) Special Publication - The Paleontological Society, 8 365 (1996)
  3. Zlatko Kvacek, Cestmir Buzek, and Steven R. Manchester Fossil fruits of Pteleaecarpum Weyland; tiliaceous, not sapindaceous Botanical Gazette (Chicago) (December 1991), 152(4): 522-523

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