Field of Science

Identifying Mosses with Only a Photo

A friend of a friend sent me these lovely photos of mosses from Bath, England to identify. 

So, where do we start? Well, I usually start with the features that look the most distinctive and sift through my mental card catalog of mosses to see which ones these fit. Sporophytes can be helpful for determining the higher classification for the moss, such as the order or family. 

1) The peristome teeth look to be made of many narrow filaments that are twisted at the apex, which = Pottiaceae in my mind.

Now we get to the more difficult part of moss identification. Trying to get lower than family or genus from just a couple photographs. What else can we see.

2) The leaves are topped by long, white awns.
3) Some of the leaves are folded inward. 
4) It is growing on rock or concrete. 

My tendency is to go with a common species that doesn't contradict the observations we can make from the photos. So my initial thought for this one is Syntrichia ruralis, but that is a species I know from North America and we know this photo was taken in England. 

So, does Syntrichia ruralis grow in England or do they have different Syntrichia species we should consider?

They have 13 species/subspecies of Syntrichia listed.
{With additional clicking there are actually only links to pages for 7 species/subspecies.}

They have two subspecies of Syntrichia, but both of them say that capsules on this species are rare. And this specimen has a lot of capsules. So I'll flip through some of the species and see which ones match. They also have great maps in the corner so I pulled up the location of Bath to see if that would help narrow the search.  

There are a few that look close, but none that give me that gut feeling of yes we have a match. The awns in the descriptions/drawings seem too short compared to the photos. They look to be at least 1/2 the length of the leaf lamina in the photos. So let's take a step back. A lot of the Syntrichia species were formerly in the genus Tortula, which is also in the Pottiaceae. Let's take a look at some of the species in that genus. 

Most of the Tortula species have small awns or are lacking them, except for Tortula muralis. 
Check the description of this species out to see what you think compared to the photos.

Long awn - Common species growing on mortared walls - Distribution covers Bath 
Nothing from the description is in contradiction to what I can see from the photos. It also points out that Syntrichia species are often larger and the photos look smaller, more similar to the Tortula in size.  

I think we have a winner! Tortula muralis is my ID for this species based on the photos and the British Field Guide.

What do you think? Would you give it a different name?