Showing posts with label parental care. Show all posts
Showing posts with label parental care. Show all posts

Thursday, January 26, 2012

Oldest Dinosaur Nursery

UTM professor Robert Reisz and his team unearthed this skull of adult and complete embryo of the Early Jurassic (190-million-year-old) dinosaur Massospondylus in the South African nesting site. Photo courtesy of Robert Reisz.

An excavation at a site in South Africa has unearthed the 190-million-year-old dinosaur nesting site of the prosauropod dinosaur Massospondylus-revealing significant clues about the evolution of complex reproductive behaviour in early dinosaurs. The newly unearthed dinosaur nesting ground predates previously known nesting sites by 100 million years, according to study authors.

A new study led by University of Toronto Mississauga paleontologist Robert Reisz, with co-author, Professor David Evans of ecology and evolutionary biology and the Royal Ontario Museum, along with a group of international researchers, describes clutches of eggs, many with embryos, as well as tiny dinosaur footprints, providing the oldest known evidence that the hatchlings remained at the nesting site long enough to at least double in size.

At least 10 nests have been discovered at several levels at this site, each with up to 34 round eggs in tightly clustered clutches. The distribution of the nests in the sediments indicate that these early dinosaurs returned repeatedly to this site, a behaviour known as nesting fidelity, and likely assembled in groups to lay their eggs, (colonial nesting), the oldest known evidence of such behaviour in the fossil record. The large size of the mother, at six metres in length, the small size of the eggs, about six to seven centimetres in diameter, and the highly organized nature of the nest suggest that the mother may have arranged them carefully after she laid them.

"The eggs, embryos, and nests come from the rocks of a nearly vertical road cut only 25 metres long," said Reisz, a professor of biology at U of T Mississauga. "Even so, we found ten nests, suggesting that there are a lot more in the cliff, still covered by tons of rock. We predict that many more nests will be eroded out in time as natural weathering processes continue."

The fossils were found in sedimentary rocks from the Early Jurassic Period in the Golden Gate Highlands National Park in South Africa. This site has previously yielded the oldest known embryos belonging to Massospondylus, a relative of the giant, long-necked sauropods of the Jurassic and Cretaceous periods. (View a video of the excavation.)

"Even though the fossil record of dinosaurs is extensive, we actually have very little fossil information about their reproductive biology, particularly for early dinosaurs," said  Evans (pictured left, bottom, with Reisz, above), associate curator of vertebrate palaeontology at the Royal Ontario Museum. "This amazing series of 190 million year old nests gives us the first detailed look at dinosaur reproduction early in their evolutionary history, and documents the antiquity of nesting strategies that are only known much later in the dinosaur record."

The study, co-authored by Drs. Hans-Dieter Sues (Smithsonian Institute, U.S.), Eric Roberts (James Cook University, Australia), and Adam Yates (University of the Witwatersrand, South Africa), is published in the Proceedings of the National Academy of Sciences.

Citation
R. R. Reisz, D. C. Evans, E. M. Roberts, H.-D. Sues, & A. M. Yates. Oldest known dinosaurian nesting site and reproductive biology of the Early Jurassic sauropodomorph Massospondylus. Proceedings of the National Academy of Sciences, 2012; DOI: 10.1073/pnas.1109385109

Tuesday, November 29, 2011

Arizona Black Rattlesnake Maternal Care

Howdy Herpers,

Before I launch into the meat of the missive, I want to first describe Melissa Amarello's mentality in the early days of our association. Our first solo outing together occurred in March of 2004. I was poised to take her to some of my "hands off" atrox dens. But she put the kabong on that idea when she indicated that she wanted to go somewhere where we could actually grab and process snakes.

That left me only one option: The Suizo Mountains. Anything and everything else under my watch was, and mostly still is, hands off.

And so our first mission was one of war on the snakes. On that day, Melissa earned the nickname "Hurricane Melissa," for she found three atrox and a female tiger rattlesnake. I found two tortoises.

The atrox she found were to become males CA54 and CA55--also known as "Doublenicks," and later, "The Road Warrior." Some of you may remember Doublenicks as the snake that eventually became a DOR. The female atrox that Melissa found became CA56. All three snakes were PIT tagged and released. Only CA55 was ever captured again.

I've attached a photo that Melissa took from that day. It is of Doublenicks perched on top of CA56, in a behavior called "Stacking." It remains to this day the best image I've ever seen of the behavior. Stacking is in essence a male's way of "hiding" a female from other male interlopers.

Melissa, her partner Jeff Smith, Young Cage and I all share a secret in the blackest parts of our hearts. Young had an atrox den that was known as "Jason's Den." Melissa and Jeff were starting to turn the corner on their mentality towards processing rattlesnakes. They wanted to study a den in hands off fashion. The four of us met, discussed strategy, and off they went to do their study on Jason's Den.

This den "was" a Cinderella kind of den. It "was" a wide open affair, where as many as 14 atrox could be observed all winter long. In terms of a den that "was" easy to study, this "was" the best to ever cross my path.

The key word is "was." Jason's Den no longer exists. Some murderous swine found the den, and in an act of senseless and wanton slaughter, ripped some bloody geysers through the snakes with their shotguns.

A few were left. They came back and got the rest. It was all carefully documented, but none of us can bear to show the pictures, or write about the heartbreak of it all. I still tear up thinking about it, but like so many things in life, I'm powerless to do anything about it.

Every year, atrocities that make this seem like kissing a pretty girl occur in this not-so-great country of ours. This is because of ignorance, and greed. While we can't do much to combat greed, we can at least educate the public to the fact that snakes do much, much more than just sit around and look at each other. If we can do everything  in our power to cast snakes in a better light, perhaps one day the rest of the world will catch on.

Melissa and Jeff are doing this very sort of thing with Arizona black rattlesnakes. I think the time has come to share some of this with you. Please click on the link at the bottom of this email, watch the video, and look at the stills. Do click one more link off to the side, the one under October that is entitled "A Rattlesnake Helper."

In closing, in many ways, some of those who study rattlesnakes are the rattlesnakes' worst enemy. People doing these studies cringe at the thought of presenting snakes as anything more than primitive wind up toys, the key being a physiological chemical reaction to queues around them--a hard-wiring at birth--instinct driven.

The ability to actually think can not happen, it's all instinct. This is the type of thinking that is never going to advance rattlesnakes in the eye of the public. It is also the type of thinking mostly done by those who have never actually taken the time to watch them.

I hope you all enjoy this video as much as I did. It is by far the best observational work I've ever seen.
We can only hope for more of this sort of thing in the future.

Best to all, roger

http://socialsnakes.blogspot.com/2011/10/day-in-life-of-rattlesnake-family.html

Tuesday, November 22, 2011

Parental Care in Horned Dinosaurs

KINGSTON, R.I. – November 21, 2011 – A nest containing the fossilized remains of 15 juvenile Protoceratops andrewsi dinosaurs from Mongolia has been described by a University of Rhode Island paleontologist, revealing new information about postnatal development and parental care. It is the first nest of this genus ever found and the first indication that Protoceratops juveniles remained in the nest for an extended period.

The findings were reported in the most recent issue of the Journal of Paleontology.

David Fastovsky, URI professor of geosciences, said the bowl-shaped nest measuring 2.3 feet in diameter was found in the Djadochta Formation at Tugrikinshire, Mongolia.

“Finding juveniles at a nest is a relatively uncommon occurrence, and I cannot think of another dinosaur specimen that preserves 15 juveniles at its nest in this way,” he said.

The analysis of the 70-million-year-old nest by Fastovsky and his colleagues found that all 15 dinosaurs – at least 10 of which are complete specimens – were about the same size and had achieved the same state of growth and development, suggesting they represent a single clutch from a single mother. The discovery also indicates that the young dinosaurs remained in the nest through the early stages of postnatal development and were cared for by their parents.

Protoceratops grew to about 6 feet long and may have taken as long as 10 years to reach full size. Those Fastovsky found in the nest were likely less than one year old when they died.

“I suspect that the preserved animals were rapidly buried by the shifting, accumulating sands that must have constituted the bulk of sedimentation in this setting,” he said. “Death likely occurred during a desert sandstorm. My guess is that the initial and present-day dryness contributed significantly to the superb preservation, not just of Protoceratops, but of all the fossils from this unit.”

Fastovsky calls Protoceratops “a fascinating and unexpected mass of contradictions.” It is an herbivore that lived in a sand sea much like the Sahara Desert and likely bestowed significant parental care on a relatively large number of offspring, perhaps because it lived where mortality was quite high.

A wide variety of theropod dinosaurs lived in Mongolia at the time, some of which, including the notorious Velociraptor, probably ate young Protoceratops’.

“Juvenile Protoceratops mortality may have been rather high, not only from predation but from a potentially stressful environment, and large clutches may have been a way of ensuring survival of the animals in that setting,” he said. “Nonetheless, if preservation is any indicator of abundance in life, then during the time represented by the Djadochta Formation, Protoceratops were a very common feature of Mongolian Late Cretaceous desert landscapes.”

Photo courtesy of Dr. Kh. Tsogtbaatar.

Fastovsky, D. E., D. B. Weishampel, M. Watabe, R. Barsbold, Kh. Tsogtbaatar & P. Narmandakh. 2011. A Nest of Protoceratops andrewsi (Dinosauria, Ornithischia). Journal of Paleontology, Nov 2011 DOI: 10.1666/%u200B11-008.1

Thursday, September 8, 2011

Remarkable Reproductive Behavior in Dwarf Hemiphractids.

Flectonotus fitzgeraldi. Female w/eggs. JCM
Five species of Dwarf Marsupial Frogs of the genus Flectonotus are found in Northern South America and Brazil. It now appears that they from two groups of species and each group forms a genus. These unique little frogs have females carry their eggs in dorsal pouches (hence the name marsupial) until the tadpoles hatch, at which time the female frogs deposit the tadpoles in leaf axial pools. Duellman et al. (2011) report observations on the reproductive behavior of Fritziana goeldii (Brazil) and Flectonotus pygmaeus (Venezuela) females that shows significant differences. A pair of goeldii goes into amplexus, the female replaces a mucus mass that is beat into foam by the male's hind feet, and while this is happening the skin on the female's back is stretched out by the male's front feet. As the eggs are laid, the male fertilizes them and moved them forward into the foam mass. Once the eggs are laid, the male abandons the female and she is left with a foam mass and the eggs on her back. Over the next 4 to 8 days the egg sac forms, apparently by her skin growing around the egg sac. The female did not start to forage for food until the sac was covered. At this time the eggs cannot be removed without injuring the female. The embryos develop during the next 17-23 days, at which time the female enters a water filled bromeliad tank and sloughs off the entire egg sac. Skin folds are visible for a few hours, but then disappear. The tadpoles escape the egg sac and feed on its remains as well as on other debris in the bromeliad tank, but tads that ate nothing metamorphosed in the same about of time. Metamorphosis is complete within the next 21 -25 days

Flectonotus pygmaeus, on the other hand actually has a fold of skin that forms a pouch and during amplexus, the female releases the mucus secretion, the male beats it into a foam, and as the eggs are laid, the male pushes the eggs into the skin folds - the pouch. The eggs are closely packed together but there is no egg matrix, and the eggs can be removed- they are not attached to each other. The female started to forage within 24 hours. After 23-26 days egg sac starts to split and the female transfers the tads to a leaf axial pool. She submerges a third of her body and the tadpoles swim out. The tadpoles do not feed, they continue to metamorphosis using stored yolk for another 11-17 days.

The authors remove the three species of Brazilian Flectonotus and reassign them to the genus Fritziana. The entire article can be found on-line.

Citation
Duellman, W.E., K.-H, Jungfer, and D. C. Blackburn 2011. The phylogenetic relationship of geographically separated “Flectonotus” (Anura: Hemiphractidae), as revealed by molecular, behavioral, and morphological data. Phyllomedusa, 9:15-29

Monday, August 1, 2011

Rapid Evolution in Island Frogs

Fanged frog guarding eggs. Photo credit:
Jimmy A. McGuire
Scientists led by Ben Evans of McMaster University have documented the rapid evolution of new fanged frog species on the island of Sulawesi, near the Philippines. The team found 13 species of fanged frog on the island, nine of which hadn't previously been described. The species differ in body size, amount of webbing in their feet, and even how they raise their young—all in accordance with the demands of their distinct ecological niches. Sulawesi has the same number of fanged frog species as the Philippine archipelago. "We would expect to find more species on the archipelago because it's so much larger, but that's not the case," Evans said. Why such diversity on the smaller island? There's less competition on Sulawesi, the researchers say. Fanged frogs in the Philippines have to compete with another genus of frogs, Platymantis. Platymantis never made to hop over to Sulawesi, leaving the fanged frogs free to spread out into new habitat niches, to which they eventually adapted. The rapid evolution of these frogs is a striking example of adaptive radiation—a concept Charles Darwin famously recorded in Galapagos finches.

Mohammad I. Setiadi, Jimmy A. McGuire, Rafe M. Brown, Mohammad Zubairi, Djoko T. Iskandar, Noviar Andayani, Jatna Supriatna, Ben J. Evans. Adaptive Radiation and Ecological Opportunity in Sulawesi and Philippine Fanged Frog (Limnonectes) Communities. The American Naturalist, 2011; 178 (2): 221 DOI:10.1086/660830