Tag Archives: Evolution

Speculative Biology Sunday: Pachyodoben

6 Feb

A lone Pachyodoben sleeps on a riverbank. Person to scale.

Pachyodoben (meaning thick walrus-face) was the largest genus of the herbivorous amphibians from the Mid-Triassic. They were semi-aquatic, inhabiting rivers, swamps and estuaries. They foraged for browse and roots during dawn and dusk, keeping cool in the water during the heat of the day and sleeping by the riverbank at night. Easily recognisable by their armoured backs, short tusks, stubby tail. For its time it was the largest herbivore ever, weighing in at two to three and a half tonnes.

There ancestry seems to come from the big headed, squat bodied Dissorophidae of the early Permian, but where in their evolution they switched to herbivory is unclear. One of their key adaptations for herbivory is their stunning ability to fake heterodonty, having both tusks and grinding ‘molars’ made from bone. Their only teeth as small and peg-like, used for stripping foliage.
The ‘molars’ seem to have been a key adaptation for switching to herbivory, as only the larger species otherwise use gastroliths to facilitated the breakdown of vegetable material.

Most of the larger species of Pachyodoben fed more on roots than low browse, and dug for them with their tusks. There is even evidence of them using their bulk to topple trees to unearth the fossial fare.

Adults were too large to be bothered by predators, even the young were well armoured enough to keep terrestrial carnivores at bay, but there is evidence of the young being preyed upon by Xenacanthidan sharks, tearing at their vunerable underbellies from beneath the surface; Mothers always putting themselves between their young and the deeper water, with red spots on their belly warning of violent retaliation should the sharks be willing to try anything.

Speculative Biology Sunday: Fruiting Larch

19 Dec

The Fruiting Larch is a frost hardy tree native to the plains of Siberia. It is a medium-size to large deciduous coniferous tree reaching 20-50 m tall, with a trunk up to 1 m diameter. The crown is conic when young, becoming broad with age; the main branches are level to upswept, with the side branches often pendulous. The male and female cones are borne separately on the same tree; pollination is in early spring with the cones taking around 7 months to ripen.
The female cones are consistently reddish to purplish through maturity and don’t harden off like other pine cones. The seed scales stay somewhat swollen and contain relatively high amounts of starch and thus are somewhat palatable, though still taste distinctly of fresh cut pine.
The seeds of the fruiting larch are not dispersed by wind as their ancestors were, but remain firmly attached to the seed scale of the cone. This way the seed is passed through the digestive tract of the birds when the cones are picked apart and eaten and thus spread further than the wind dispersal employed by other conifers.
The fruiting larch has become an important food source for the animals in the coniferous ecosystem. Many birds and mammals feed on the seed scales which ripen at the beginning of autumn and are important for animals building up food reserves before migrating south or going into hibernation.
Most notable of these is Grims Cuckoo, who feed almost exclusively on the cones throughout autumn and will only migrate south once they run out which is usually almost midwinter, making them very important seed distributors.
Fruiting Larch are almost dominant in areas recently cleared by fire or permafrost thaw, but are gradually out-competed by other evergreen conifers over time.

TYFYT

Speculative Biology Sunday: Seacad

5 Dec


Hooray for a new SBS! Don’t you all just love reading the massive slabs of text I write out under these things. I got the idea for this one when I was at the coast, there were cycads everywhere and I enjoyed that fact very much. And of course I began to wonder what cool things cycads could or could have done throughout their evolutionary history. I’m not sure whether the seacad is alternative evolution or future evolution, because it could actually be both; either a future evolutionary development or an extinct form from the height of their diversity which we haven’t found fossils for. Anyway, on with the show.

The Seacad
Seacads are a monophyletic group of cycads which thrive in sandy soils and are highly tolerant of salinity. Found in tropical and subtropical regions throughout the world their origins are clouded due to their ocean spanning dispersal mechanisms, though most botanists agree they fit into the family Zamiacea.
They are perennial, evergreen, and dioecious.
They have tall and erect, usually unbranched, cylindrical stems, and stems clad with persistent leaf bases.
Their leaves are simply pinnate, spirally arranged, and interspersed with cataphylls. The leaflets are sometimes dichotomously divided. The leaflets occur with several sub-parallel, dichotomously-branching longitudinal veins; they lack a mid rib. Stomata occur either on both surfaces or undersurface only.
These traits however, are not what characterize the seacad. They produce drift seeds.
The seeds and the expanded thickened lamina (the outer part of the cone; the lighter brown bit) of the the seacad are highly buoyant and sealed against seawater. This allows them to disperse over staggering distances using ocean currents.
Seeing that the best chance for the seed to grow to maturity is to colonise a new beach the seed will sit in the cone of the parent plant until a rain event or storm when they have the best chance of being washed out to sea. When the lamina are wetted, they swell up and this sudden increase in volume pops them from the cone to be washed down the beach and out to sea.
As they are diecious (having seperate male and female plants seperate) the male and female seeds alternate spirally throughout the cone, assuring where there are two seeds attached to a lamina they will be able to reproduce should they both germinate on some foreign shore.
They grow best in partial shade. If you’ve read through this far then you are a very special person indeed.
If you enjoy speculative biology and evolution, you should check out this forum. Lots of great people with unique ideas. Also the competitions are pretty fun. Be sure to vote for my entries in the competitions if you do sign up, it would be muchly appreciated.

TYFYT

Speculative Biology Sunday: Lowland Panidaru

14 Nov

The Lowland Panidaru is both the largest and most widespread species of Panidaru. They inhabit most lowland areas in and around the Indo-Papuan Plateau. They reach their densest populations in riverine areas where forests meet the floodplains of the North Eastern Australia.
They are descendant from the subfamily of New Guinea Spiny Bandicoots and since then have evolved and atrophied scansoriality and arboreality and become strictly herbivorous.
The maximum size of a male Panidaru can be over 2500 kilograms, though females rarely exceed a weight of 1800 kilograms. They are knuckle walkers and use their hands to manipulate and collect food, with their syndactyl second and third digits opposing the forth and fifth digit with the first digit being atrophied into obscurity. Their coats are a dark shade of brown with lighter undersides, males often black. The sport modified hair which form a spiney barricade across their hindquarters, often with stray pieces of litter that get lodged there when an individual squats down to feed.
Their domed head mistakenly suggests a large braincase, however this is merely due to a pronounced sagittal crest and attached jaw muscles which allows the Panidaru to grind up tough vegetation with ease.
They prefer feeding mainly on soft browse, leaves, shoots and fallen fruit, though are not unknown to take tougher vegetation or dig for tubers. Occasionally when deficient in certain minerals or salts they can be observed eating leaf litter and soil. The floodplain Panidaru have a particular daily migration and feeding behaviour. Spending the night in the forested areas they forage around the jungle they spend their mornings foraging through the forest, mostly searching out their favourite fruits. One particular fruit is so favoured by them it has earned their namesake, Panidaru apples.
After spending their mornings foraging in the forest they will move out into the wet floodplains to graze on the lush grasslands. They also take part in all social interaction in the grassland, such as females strengthening social bonds with other females, searching for mates and males settling territory and mating disputes. They also excrete the now inoculated and scarified seeds of the Panidaru apple, which are important for the colonisers for the forest ecologies.
Panidaru have two key adaptations which have allowed them to outcompete placental analogues.
The first being that they taste terrible, which deters predators. On their necks and running down their chest they have two large modified sweat glands that secrete a mild toxin which tastes terrible and induces vomiting when injested and occasionally death in smaller carnivores.
The second being that they can have different sets of offspring in development. At the same time a single female can simultaneously be raising one almost independent offspring out of the pouch which still may be suckling, one suckling “jellybean” neonate young sucking and one fertilized egg developmentally halted until the “jellybean” young has started to leave the pouch. Which means that populations can bounce back from hard times faster than their placental competitors.
It is colloquially known as the Marsupial Gorilla, though ecologically more analogous to the modern Indian rhinoceros.

TYFYT

Pinnacle of Evolution

22 Jul

The quotes are actually from our lecturer for Evolution of Biodiversity, during the introductory lecture. I simply put two and two together, which everyone knows equals RHINOCEROS BEETLES ARE AWESOME. I’m good at maths. The course is shaping up to be amazingly awesome. I’ve been pumped for ages for it because I thought it was going to be awesome but it is actually exceeding my expectations. We have a really good lecturer for it as well who is constantly fascinated with the content she is teaching us. Its great.

HvZ starts next week. Get to a safety meeting if you haven’t already! Should be quite the amazing. Midnight mission on the first day!

TYFYT

Speculative Biology Sunday: Arse weed

4 Jul

You have you’re very own flora, made up of thousands of species of organisms and thousands of individuals, most microscopic others less so. Kingdom Plantae, for the most part, seem to be missing out on this particular niche space. It only ever seems to be alga that grow on more slow moving animals such as sloths (if anyone knows any other examples, let me know.)
So here is a plant that live in and around an animal. From some undetermined point in the undetermined future.

Arse weed

The above plant is representative of the genus of plants colloquially known as “arse weeds”. Little is known about their evolutionary history, though their modern ancestors are definitely from somewhere in the Liliaceae family.
They are a bulb based plant and have long fairly broad leaves with parallel venation dominant but not exclusive.
There are usually three or four dominant “anchor roots” growing from the bulb as well as numerous other more short lived roots. These anchor roots are thick and spongey which allows oxygent to travel down to the tips of the roots. These roots also spiral around the wall of the large intestine of the animal it inhabits, and are quite springy. This is the mechanism by which the plant prevents itself from being excreted with the rest of the animals waste product.

After the plant is excreted it is anchored by the anchor roots, and after the animal has finished its business the roots recoil, pulling the plant back into place.
Arse weed is found solely in large ruminant herbivores. Seedlings have been found or observed in other herbivores and occasionally in canids, but for whichever reason these plants never thrive. The small berries produced by these plants are a remarkable white colour and highly aromatic to attract the attention of the colour blind herbivores which the plant inhabits. These berries contain a large, thick coated seed which is scarified during digestion and then germinates in the large intestine. Setting down its anchor roots is the plants first priority and only once these are set will it put any of its resources into poking photosynthetic leaves into the outside world.
Once the plant is established and thriving, a third player arrives to take part in this quirky like symbiosis, though this new arrival is somewhat more malicious. A fly seeks out arse weeds which aren’t yet flowering and takes advantage of the fact that the anus is obstructed by the plant to crawl inside and lay its eggs. These eggs hatch into parasitic larvae which feed on the flesh of the herbivore, much to its irritation. Trying to alleviate this irritation, the herbivore with try and scratch the itch against whatever it can find, usually trees, being knocked about and damaged triggers the plant to begin flowering. By the time the flowers are fully developed and ready for pollination, the fly larvae are fully developed and emerging as fully grown mature flies which then go and receive their first meal from the flowers of the arse weed.
Arse weeds are usually and annual plant as they are often dislodged after long enough.

TYFYT

Unfortunate Telling

25 Jun


Evolution isn’t always for the better.
Yeah, supposed to be packing. I have plenty of time.
I’ll be posting more often during the holidays as well, so watch this space.
To all my friends from uni, hope you all did well on all of your exams, and enjoy the holidays!

TYFYT

Speculative Biology Sunday: Gympie Crab

25 Apr

Birgus hortusportens – Gympie Crab

gympiecrab
The Gympie Crab was actually created for a competition being held on the speculative evolution forum which I regularly partake in since I started doing these. The competition in question to create the best symbiosis between two organisms. Instead of going for the beyond clichéd plant-feeds-animal, animal-protects-plant, I thought I would do a little bit of role-reversal.

The gympie crabs modern ancestor, the coconut crab, is a terrestrial hermit crab (but carries no shell as adults) which is the largest land arthropod in the world living in tropical islands of the world, mostly in the pacific. Human populations on the islands which they live throughout the world have significant negative effects on the crabs due to habitat loss and predation from people, rats and pigs. The Gympie Gympie which the Gympie crabs carry are completely identical genetically to modern Gympie Gympie, except for a slight founder effect meaning that they are generally smaller and reproduce earlier in their life history. It is a shrub native growing one to two metres tall and native to Australasia. The plants are covered with silica tipped hairs filled with powerful toxins, which commonly kills dogs and horses, and has claimed at least one human life.

At some point in the 21st century Gympie Gympie was accidentally introduced to a large pacific island inhabited by coconut crabs and humans and a mutualistic symbiosis evolved between the crab and the plant. The crab receives protection against predators as its thick exoskeleton protects it from the stinging hairs, shade allowing it to forage in the open during the day, and fruit when the plant produces it. The plant gains from this relationship because plants are always taken from shaded positions where the crab can hide while changing over his dirtball and give the plant plenty of time out in full sun where it can prosper and is also fed and watered by the excrement of the crab, and the seeds of any one plant are distributed over a wider area than if it was growing in the ground.

The crabs hold a ball of dirt between its abdomen and its cephalothorax where the roots of the plant grow, and the stem grows upwards out from the side of the crabs body. Should the shrub grow too tall the crabs will drop the plant and either harvest a new one or tear the top of the plant off, encouraging more lateral growth which is better for the crab.

The Gympie Crab as a seperate species from Coconut Crab is hotly contested as they seem to be able to produce viable hybrids. However most of the areas where Gympie Crabs are found, Coconut Crabs are not, as they have been preferentially preyed upon to the point of extinction of the ancestral form. It has also been reported that Gympie Crabs will preferentially breed with other Gympie Crabs, reinforcing the behaviour in their offspring.

TYFYT

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