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The Speculative Dinosaur Project: Xenoquercus

February 3, 2014

Spec’s flora has some notable differences from it’s HE counterpart. Among other things, older clades now extirpated on HE have survived, while clades common to both realms have produced remarkably different evolutionary paths (usually towards being exceptionally poisonous in Spec). Examples of ostensibly either can be found in the
temperate forests from Aotearoa’s South Island. In both time timelines, these ancient groves have been composed of unique plant lineages that have once dominated most of Gondwanna, but now can only be found here. In Spec, this is even more evident, as the absence of the KT event meant that several clades extinct in HE managed to survive, such as seed-ferns and southern gingkos.

Within this menagerie is one of Aotearoa’s most enigmatic plants, Maui’s False-Oak (Xenoquercus australis). Externally, Maui’s False-Oak lives up to its name: it strongly resembles a
member of the genus Quercus, which are in fact also present on Spec, being as-old-as-the-Maastrichian plants as they are. However, being absent from southern continents until the american interchange, they never got into New Zealand, making Xenoquercus‘ discovery quite a mind screw, given it’s primeval location. When it was finally studied in detail, specbotanists were pretty much relieved that it isn’t an oak, in fact not even within Fagales. However, a new problem arouse then: what exactly is Xenoquercus?

Based on genetic studies, Maui’s False-Oak is among the most basal known angiosperms. Appearently, it diverged soon after the appearence of the clade itself, and its ancestors must have had a restricted Gondwannan distribution, for they were likely never very widespread. Some specbotanists have suggested a close relationship with Amborellacea, and indeed it is possible that they are at the very least sister taxa; considering that New Caledonia and Aoteroa were fused together during the Paleogene, Xenoquercus‘ possible status as p-Amborella‘s closest relative is plausible. However, the few genetic studies that concluded such a relationship seem to indicate that this genus would have diverged from p-Amborella very early indeed, not long after their divergence from the rest of Angiospermia, and unlike its new caledonian relative it isn’t dioecious, as an individual plant has both female and male flowers.

Xenoquercus is endemic to South Island, though subfossil polen records suggest that a close relative (p-Xenoquercus [?a.] meridionalis) occured in North Island, later disappearing as late as 2000 years ago. The causes for such sudden extinction aren’t well established, but it seems it was fairly rare since the beginning of the late Pleistocene, and some natural hazards might have eventually wiped the remaining plants out, specially considering most of its population was seemingly restricted to some forest pockets in the North Island peninsula. Precisely at the same time of its possible sister species’ began to disappear, Maui’s False-Oak seemingly started to spread: it briefly managed to establish itself on southern North Island, but eventually disappeared, with no reccords younger than 300 years ago. All that can be currently be said with certainty is that the two known species of Xenoquercus had different distribution patterns: whereas X. meridionalis was a mainly a subtropical denizen that could usually be found close to members of its species, forming forests mainly composed of its species, X. australis prefers colder temperatures, and is seldomly found near members of its kin, with an individual tree sometimes being kilometers away from another one, though in a few areas they do occur in reasonably large numbers, even forming cohesive forests.

The possible reason for these different distribution patterns between the Xenoquercus species was probably resulted from their reproduction. Xenoquercus, like Amborella, has its flowers organised in terminal cymose inflorecenses, and unlike more advanced angiosperms there is no clear distinction between petals and
sepals, and they are arranged in a spiral. The flower has a structure clearly very similar to that of Amborella, though like more derived flowering plants it has stamens on filaments and syncarpous ovaries. The petal/sepals are brightly coloured, and the colour varies within members of the species. Yellow, orange, pink, red and purple are the most common colours, though green and blue aren’t unheard off. At least 12 polinators are known, the majority of which are birds (some species, like the tweety Kalimantornis xenoquercophaga,
feed exclusively on False-Oak nectar, while others like Cracticavis novazelandica prefer the tree’s nectar but aren’t by no means dependent on it to survive), with at least two volaticothere species and several insects and even one lizard (Urogecko quercophilus) as polinators as well. Once polinated, the ovaries become a chestnut sized fruit called “nut-acorns” (alternatively called “heart-fruit”). The name is somewhat misleading, since its not a “nut”, but a juicy, bright coloured fruit (identical in colour to the tree’s flowers) somewhat similar to a peach in texture and taste, though the seeds are much smaller and similar to those of an orange.
These fruits are targeted by a few animals, but it is believed that the intended target is the Aotearoan Sifaka (Callaeopithecus apteryx), a secondarily flightless elphaba that glides around in the forest canopy. The
tree produces a potent smell that quickly spreads across the forest once the fruits are developed; because birds and (most) volaticotheres have a poor sense of olphaction, the first animals to reach the tree are the primates, quickly followed by large frugivorous birds. Pseudomysticine volaticotheres also have a fairly accurate sense of smell compared to their aerial insectivore cousins, being terrestrial omnivores as they are, and they often climb trees at nighttime to get those fruits. The plant has no specific reproductive season, so fruits and flowers are availiable year long.

Because of the known distribution of animals specialised in eating flowers and fruits of Maui’s False-Oak – the Aoteroan Sifaka, for example, was never present in north island, but other elphabas are -, it is possibly safe to assume X. meridionalis probably didn’t had such a large “fan base” as its modern relative. Because sadly no remains other than the tree’s polen survived to the modern days, one can only speculate if the tree’s fruit was more acidic and less “tasty”, the lack of known animals that consumed the fruit being a possible explanation for the
tree’s less wide distribution and eventual extinction. A similar thing happenned to gingkos on HE: unlike Spec’s gingkos, which have some mammals that feed on their “fruits” and helped them to spread around, HE’s had no known consumer of their fruits in the Cenozoic, so they had more trouble to spread around and virtually died out in the Pleistocene.

6 Comments leave one →
  1. February 6, 2014 6:16 pm

    Awesome đŸ˜€

    So NZ mustn’t have any non-avian dinosaurs? Just asking

    • February 6, 2014 6:48 pm

      I’m going to say no: like in HE, all native dinosaurs are birds. However, there’s a higher mammal diversity, what with the two local primitive cancridonts, the gondwanatheres, volaticotheres and a flightless elphaba.

      • February 7, 2014 9:17 am

        Interesting…

        So how did the native, notoriously generalist and very hard to kill ornithopods and random coleurosaurs die out?

        I tend to think that they won’t die out and will just continue on adapting, perhaps towards a more semiaquatic or alpine lifestyle once Zealandia starts to sink and shrink…

      • February 7, 2014 11:04 am

        Same way land mammals and crocodylomorphs died out in our world, if they don’t die by lack of resources on the vestigial isles.

  2. February 8, 2014 6:24 pm

    I see… Goddammit Zealandia is quite mysterious in its extinctions…

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