Iain Reid, of Wakari, asks :-
The conifer family Podocarpaceae is the oldest of the living conifer families, as in circa 230 million years ago. The modern podocarp’s have seeds distributed by birds, so what was around back then to distribute the seeds assuming birds hadn’t yet evolved?
Janice Lord, a botanist at the University of Otago, responded.
The Podocarps include iconic New Zealand trees such as Totara, Rimu, Kahikatea, Miro and Matai, as well as species in Australia, South Africa and South America.
While the podocarp family is old, dating back to the Triassic-Jurassic with fossils distributed in both northern and southern hemispheres, living species are all of recent origin (mid-late Cretaceous, c.120 million years ago) and over-whelming southern in their distribution.
There is no guarantee that ancient podocarps were fleshy fruited like the podocarps we are familiar with today, as after all, their closest “sister” group (Araucariaceae) contains trees such as Kauri, Chilean Monkey Puzzle and Australian Bunya, which are not fleshy fruited. However it is quite clear that plants and animals were involved in seed dispersal mutualisms prior to the evolution of birds.
Cycads and the maidenhair tree Ginkgo biloba, for example, both have fleshy fruit. Cycads have a fossil record dating back at least 280 million years, so the same age or older than the podocarp family, and the genus Gingko dates back about 190 million years. To put this in context, Archaeopteryx, considered by many to be the first bird, is about 150 million years old, and birds of modern form don’t appear in the fossil record until the late Cretaceous, about 100 million years ago.
Prior to this though, there were enormous herbivorous dinosaurs such as Diprotodon which could have reached into tree canopies to strip fruit from branches, as well as smaller tree-climbing dinosaurs such as the Scansoriopterygids, and the recently discovered Pegomastax africanus that was thought to specialize on fruit. How many fruits these animals ate, and how effectively they moved the seeds to new areas is very hard to determine as fossilized dinosaur dung (coprolite) is exceedingly rare.
Until paleontologists find more dinosaur dung, we will know next to nothing about ancient fruit dispersal.