Friday, May 12, 2017

#30 Where do they think snakes came from

This question comes in from Jacob.

The origin of snakes is relatively well researched and has some surprising, at least to me, members of the snake family. I think we should start by defining what makes a snake a snake and then look at the fossil record.

All snakes belong to a clade known as Ophidia which includes snakes and those extinct animals more closely related to snakes than other non-snake squamates (what most people would call lizards are non-snake squamates). Interestingly, more and more evidence is mounting to include members of the Mosasaur family within snakes as they share many characteristics with pythons, more on this later. The appearance of the Ophidia clade is suggested to lie in the early to mid Cretaceous period (145-65 million years ago). Characteristics of modern snakes, but not all snakes, includes scaled skin, limblessness (not entirely true for pythons, boas and extinct species), moderate to extreme extension of the thorax, and decrease in the number of cervical, lumbar and pelvic vertebrae.

Fossil evidence:
Tetrapodophis amplectus from http://www.sci-news.com

Snakes have a somewhat spotty fossil record. Delicate bones and the large number of ribs with a lack of more robust leg bones, or robust skulls leads to the rarity of snake fossils. However, many do exist and allow for significant, if not total, understanding of the origin of snakes. In fact, the earlier mentioned 145 million years ago is in the process of being disproven with a recent discovery in Alberta that may be as old as 167 million years. The skulls of these new species place them firmly in the snake classification. Another fossil, which is younger, Tetrapodophis amplectus, is a four legged animal that has all the body features of a snake in addition to having four limbs. The overlap between limbless fossils and those with two or four legs that all bear the derived anatomy of snakes makes a very tangled picture. However, it is not uncommon to have this kind of variability in the evolutionary process. Though two theories have been hotly debated, burrowing vs marine swimming, the burrowing theory is finding support from CT scans. These suggest snakes lost their limbs to burrow.

Mosasaur from the Oceans of Kansas collection: http://oceansofkansas.com/mus-mosa.html

When snakes have legs...:
Not all snakes, fossil or modern, are limbless. Modern members of the python and boa family have a structure called pelvic spurs. These spurs are remnants of their leg bones, referred to as vestigial structures. I discussed snake legs in a previous post about limbs. Cornell University has a short video about snake toes. Then we have the ancient marine reptiles of the Mosasaur family. Research is building to show that they at least share a more recent common ancestor with snakes than other reptiles while other research suggests that they might in fact be snakes.

So where does that leave us...
Research suggests that snakes evolved from burrowing lizards. Based in the fossil record there seem to be multiple species with legs that possess many of the derived characters that make a snake a snake. This information gives weight to the idea that snakes are evolved from a much earlier lizard which would have had four limbs. These limbs were later lost, mostly, but retained in full, perhaps, by the mosasours and partially until the modern time in the pythons and boids. In reality, scientist are still combing the fossil record and DNA, in the form of comparative genomes, to produce a complete family tree for snakes and their ancestors. Even venom origins are helping paint a better picture of snake evolution.

Wednesday, November 4, 2015

Species Spotlight: Desertas Wolf Spider


Name: Desertas Wolf Spider
Scientific Name: Hogna ingens
Conservation status: Critically Endangered
Location: Desertas Islands Portugal
Habitat: Mixed grasslands with exposed rocks and soils
Diet: Predator; invertebrates and lizards

Additional information: The Desertas Wolf Spider is the world's larges wolf spider with a leg span of 3-5 inches. With no mammals on the island this spider is the top predator in its environment. Decline of this spider is caused directly by invasive grasses which root in the crevasses needed for the spider, and other wildlife native to the island, to make homes. Current conservation efforts are underway to move populations of the island's wildlife to areas without the invasive grasses and to remove the invasive grass as well.

Resources:
IUCN Red List
EOL
Animal Arkive

Friday, October 30, 2015

Species Spotlight: Lemur Leaf Frog

Name: Lemur Leaf Frog
Scientific Name: Hylomantis lemur
Conservation status: Critically Endangered (Extirpated from many sites particularly in Costa Rica)
Location: Central America (Panama, Columbia and Costa Rica)
Habitat: Undisturbed Humid Forest
Diet: Unknown though small invertebrates are most likely diet.

Additional information: The Lemur Leaf Frog changes color depending on activity level and time of day. This frog is one of few species that can bask in sunlight for long periods of time without drying out. Pterorhodin pigment in the skin allows it to reflect heat and may add to disease resistance. The resistance of this tiny frog to Chytridiomycosis, a fungal disease that is decimating many amphibian populations, is of great interest to scientists who are involved in amphibian conservation efforts around the world.

Resources:
IUCN Red List
EOL
Animal Arkive

Monday, October 26, 2015

Species Spotlight: Angel Shark


Name: Angelshark, Monkfish, Atlantic Angelshark
Scientific Name: Squatina squatina
Conservation status: Critically Endangered, extirpated from large areas of former range
Location: North Atlantic Ocean, Mediterranean Sea, Black Sea (Formerly North Sea)
Habitat: Coastal waters and outer continental shelf waters with sandy or muddy bottoms
Diet: Carnivore: fish, skates, molluscs, and crustaceans

Additional information: Angelsharks are bottom feeding, nocturnal sharks which spend daylight hours buried in muddy or sandy bottoms with just their eyes exposed. Though not a fish consumed by humans, the biggest threat to the Angelshark is fishing. Their decline is caused because these sharks become by-catch, unused fish caught and often killed, of trawling.

Resources:
IUCN Red List Entry
EOL Entry
Animal Arkive Entry

Monday, October 19, 2015

Species Spotlight: Short-eared Dog



Name: Short-Eared Dog (Short-eared Zorro)
Scientific Name: Atelocynus microtis
Conservation status: Threatened/Endangered
Location: Peruvian Amazon Rainforest
Habitat: Undisturbed Rainforest
Diet: Generalist; fruits, fish, mammals, insects, frogs, crabs, and reptiles

Additional information: The Short-Eared Dog has thick dense fur to stay dry while swimming and in the intense rains within the forest. The dog also has partial interdigit membranes (partial webbing) probably owing to its time spent swimming and fishing. Due to being extremely reclusive the exact numbers in the wild are unknown but it is suspected that there are less than 15,000 left in the wild.

Resources:
IUCN Red List Entry
Animal Arkive Entry
Encyclopedia of Life Entry

Saturday, October 10, 2015

Species Spotlight: Sea Pigs



Name: Sea Pig
Scientific Name: Scotoplanes sp.
Conservation status: Unknown but threatened by deep sea trawling
Location: Atlantic, Pacific and Indian Oceans
Habitat: Deep sea >1000m
Diet: detritus and scavenged corpses

Additional information: Sea pigs have a very sensitive sense of smell that they use to locate food. The appendages, including those coming from the animal's back, are legs. Sea pigs are echinoderms, related to starfish and sea urchins, and are a type of sea cucumber. These animals have been cited as a possible source for figuring out the life style of the fossil Hallucigenia from the Burgess Shale deposits.

Resources:
Encyclopedia of Life Entry
Facts from WIRED Magazine
From Echinoblog

Wednesday, September 30, 2015

Species Spotlight: Fossa


Name: Fossa
Scientific Name: Cryptoprocta ferox
Conservation status: Endangered
Location: Madagascar
Habitat: Dense forests and woodlands
Diet: Carnivore; lemurs, rodents, frogs, lizards and birds.

Additional information: Despite its feline appearance, including retractable claws, the Fossa is the largest member of the mongoose family that can grow to over 2 feet long and close to 30 lbs. The Fossa specializes in hunting lemurs. Due to its forest habitat requirements this species has seen a population drop of 30% over the past 20 years as Madagascar rainforest is cleared for agriculture and by logging. It is also often targeted by locals for eradication because it will prey on domestic fowl.

Resources

Wednesday, September 23, 2015

Species Spotlight: Pink Fairy Armadillo


Name: Pink Fairy Armadillo
Scientific Name: Chlamyphorus truncatus
Conservation status: Unknown/Data deficient
Location: Argentina
Habitat: Desert, and dry, sandy grasslands
Diet: Worms, insects, snails and grasses

Additional information: The smallest of the armadillo species, measuring 3-4 inches long on average. Nicknamed the "sand swimmer" for its extraordinary speed and efficiency when it comes to burrowing. Listed as Data Deficient; little is known about its population status, ecology or requirements. Due to its capture for black market pet trade and the fact that it has a poor survival rate in captivity it is a priority species for future assessment studies.

Resources:
IUCN Red List Entry
Animal Arkive Entry

Sunday, September 20, 2015

Species Spotlight: Maui hesperomannia


Common Name: Maui hesperomannia
Scientific Name: Hesperomannia arbuscula
Status: Critically Endangered
Type of plant: Shrubby tree
Habitat: Lowland rainforests
Range: Maui and Oahu

Additional information: This distant relative of the Magnolia resembles a more familiar plant, rhododendrons, in growth and shape. Only 25 individuals are thought to remain of this beautiful plant. The biggest threats come from feral pigs, introduced rats, invasive plant species, trampling by humans and human collection of specimens. Several botanical gardens are propagating this plant to help with species survival.
Animal Arkive
EOL
IUCN Red List

Wednesday, September 16, 2015

New Resources - Let's learn MATHS!!

I will still be answering questions as I receive them, however, I have been asked to add something additional. As we move forward I will be adding resources for science learning in the online environment. These will not, for the most part be sites for taking classes but rather sites for learning aids or for fun science learning.

The first request was for mathematics resources, so here are some of my favorites...

Math Warehouse
This is an interactive site for students, teachers and just about anyone who needs to brush up on math concepts. The site is easy to navigate by math type or searching.

Math is Fun
Another site that covers a wide range of math topics from geometry and algebra. Each topic has a ton of images, great definitions and activities to reinforce the information. The site is easy to understand and breaks all the topics down to easy to understand and manage topics.

Math.com 
This is a self tutoring site for Kindergarten to Calculus and some other advanced topics in math. The site includes things like study tips and test prep guides as well as practice problems. It is a great all around source for learning new or brushing up on older math knowledge.

Cool Math Games
Learn basic math concepts with some fun flash games.

Numberphile
A great youtube channel that tackles complicated and interesting math topics through series of weekly videos. Also the Numberphile 2 Channel which covers many of the topics more in-depth than the main channel.

TecMath
A youtube channel that shows tricks and tips for doing math and remembering mathematical information.

Mathantics
Youtube channel to review or learn various math principles.

3Blue1Brown
Ever wanted to learn math as entertainment? Then this is the youtube channel for you. Sadly it has been almost a month since they uploaded their last video.

Mathologer
A really fun math channel that explore theories and properties with visual demonstrations.

ViHart
A really fun channel that explores math concepts with humor and a free form style that one might imagine a journal being written in. Bonus for the riotously funny sketches and images that go with it. (And it covers some other topics too.)